A real cool way if you were doing lots of these sets would be to use and old octal tube sockets with pins five and six wires to the rheostat. Then all you would have to do is just remove the tube and plug the rheostat in

A real cool way if you were doing lots of these sets would be to use and old octal tube sockets with pins five and six wires to the rheostat. Then all you would have to do is just remove the tube and plug the rheostat in

Yeah that’s what I’m thinking about because I have about a dozen RCA sets in storage none newer than 1950. Today I picked up a 1949 Emerson and a Dumont RA103-A with the FM radio and a CRT I’ve never seen before, a 15DP4. It tests great…almost new. One owner set.

Note for the trap adjustment with the VTVM across the video detector load resistor, the case of the VTVM must not be grounded to the mains supply ground. That would have to be lifted. You can be cautious and do it this way. Or alternatively if you have a digital meter that measures trends rather than just an absolute, that may be safer.

Not sure I understand what you’re saying about the VTVM. So I shouldn’t connect it directly to the 120V AC supply? Would running it through the isolation transformer help with this or am I way off base with what you’re talking about?

The isolation transformer won't help.

Look at it this way: you want to differentially measure a small dc voltage that is not referenced to the chassis ground. A three pronged plug on your VTVM, one is hot, one is neutral and the round pin is case ground. The metal case is grounded via the third pin to protect against you getting a shock if the case is not at ground potential.

If you try to connect your IM-18 VTVM to the load resistor in the next step without removing the ground pin connection on the power plug, you will short circuit the minus supply in the TV set and cause damage to the TV and likely your test equipment.

Background: in your chassis, to avoid adding a DC restorer circuit to clamp video black level, the designers used DC coupling to pass the video DC component from the video from the detector to the CRT grid through two stages of video amplification with the 12AU7 tube. To DC couple the video stages, the video detector is at about -120v DC. The -19.2v DC level on the plate of the first amplifier is coupled to the grid of the second amplifier. And the second amplifier plate at 134v DC is coupled to the CRT grid. The designers did not provide 100% DC coupling to avoid changing brightness as the 12AU7 warmed and current drifts. But the DC coupling is sufficient to give consistently good black level clamping.

You therefore must be aware that because of this design, you have to take precautions. RCA warns you a little bit. Their audience is trained electronic engineers and technicians and the warning would make them consider how to make the measurement under these circumstances. I hope this is clear and you understand. If not please ask more questions. If you do not understand the design concept of the video amplifier in this set, now is a good time to learn.

I understand the description of the danger inherent in the VTVM measurement. My VTVM does not have a ground pin on the plug, just a non-polarized plug that was standard back in the day. I’ll be very careful regardless. As for the circuitry description I am a little lost on some of it but I’ll be back with some questions after a bit of research for sure. Thanks so much for all of this knowledge and your generous time and guidance!

I should add the short circuit would occur without removing the third prong ground of the VTVM, -120v of the VTVM ground to mains ground thru the case ground of the HP8601a where the signal ground lead in turn is connected to the chassis. So you will be directly shorting out the -120v DC supply through both test equipment.

The isolation transformer won't help.

Look at it this way: you want to differentially measure a small dc voltage that is not referenced to the chassis ground. A three pronged plug on your VTVM, one os hot, one is neutral and the round pin is case ground. The metal case is grounded via the third pin to protect against you getting a shock if the case is not at ground potential.

If you try to connect you IM-18 VTVM to the load resistor in the next step without removing the ground pin connection, you will short circuit the minus supply in the TV set and cause damage.

Background: in your chassis, to avoid adding a DC restorer circuit to clamp video black level, the designers coupled the DC component of the video from the detector to the CRT grid through two stages of video application through the 12AU7 amplifier. To DC couple the video stages, the video detector is at about -135v. The DC level on the plate of the first amplifier is coupled to the grid of the second amplifier. And the second amplifier plate DC is coupled to the CRT grid. The designers did not provide 100% DC coupling to avoid changing brightness as the 12AU7 warmed and current drifts. But the coupling is sufficient to give consistently good black level clamping.

You therefore must be aware that because of this design, you have to take precautions. RCA warns you a little bit. Their audience is trained electronic engineers and technicians and the warning would make them consider how to make the measurement under these circumstances. I hope this is clear and you understand. If not please ask more questions. If you do not understand the design concept of the video amplifier design concept in this set, it is a good time to learn.

Scaring the crap out of me! I don’t want to destroy the equipment I just spent a month acquiring. My VTVM does not have a ground pin on its plug. Is my equipment safe if I use it?

If there is no ground pin it is safe to use. However you must keep safe. The VTVM case must be isolated from chassis ground as it will be at -120vdc. I keep mine away from the chassis. And do not touch the VTVM when the power is on.

You will get a very bad jolt of you are touching the chassis with one hand and the VTVM with the other. When I was young long ago, I was taught the one hand rule: place one hand in the pocket and only use the other hand to probe and test. I cannot emphasize the danger if you do not take care.

Just be methodical and understand what you are doing. You should have no problem if you just setup the VTVM, isolate the case and just observe it as you make the adjustments. Just refrain from touching it.

And the generator will be fine as long as you have a good ground connection.

If there is no ground pin it is safe to use. However you must keep safe. The VTVM case must be isolated from chassis ground as it will be at -120vdc. I keep mine away from the chassis. And do not touch the VTVM when the power is on.

You will get a very bad jolt of you are touching the chassis with one hand and the VTVM with the other. When I was young long ago, I was taught the one hand rule: place one hand in the pocket and only use the other hand to probe and test. I cannot emphasize the danger if you do not take care.

Just be methodical and understand what you are doing. You should have no problem if you just setup the VTVM, isolate the case and just observe it as you make the adjustments. Just refrain from touching it.

Thanks again! I have a very healthy, I think, respect for electricity. I do not like shocks. Doesn't matter if it's a tingle from an insufficiently discharged capacitor or a 350V DC B+ shock...I don't like them. I am especially cautious inside tube equipment. I have a 16" RCA with a metal cone CRT carrying 15kV that I'm terrified to work on. It's a shame because the cabinet for this TV is perfect. Literally owned by a little old lady who only drove it to church on Sunday's.

Took a trip up to a little town about 35 miles north of here and picked these up Sunday. Sorry, I know it's off topic but I just couldn't help it!!!

https://imagizer.imageshack.com/v2/1024x768q70/923/B6eE9X.jpg

https://imagizer.imageshack.com/v2/1024x768q70/922/acJQEl.jpg

Took a trip up to a little town about 35 miles north of here and picked these up Sunday. Sorry, I know it's off topic but I just couldn't help it!!!

https://imagizer.imageshack.com/v2/1024x768q70/923/B6eE9X.jpg

https://imagizer.imageshack.com/v2/1024x768q70/922/acJQEl.jpg

You have been infected! The bug has bitten you. Oh, welcome to the club as they say. But seriously, nice...

I started on the vintage TV thing 55 years ago this year with the late 1940's RCA. I suppose what amazes me most is in 2024 there appear to be more olds becoming available than I recal seeing 40 to 50 years ago.

I would take time travelling through the US North East and I saw very little. Now they seem to be jumping at me.

I don't know what others think.

Nice catches! I especially like the Dumont. But the Emerson is nice too!

There's no question the vintage electronics "business" has exploded in the last 5 years. Vintage audio prices have gone through the roof. It's amazing the entry level units from elite manufacturers like Marantz, Pioneer, Sansui are going for thousands of dollars on eBay. Vacuum tubes are being sucked up by tube amp devotees by the tens of thousands. Maybe that, and the ease of selling through virtual auction and market sites are prompting people to dig out Grandpop's old, heavy TV out of attics and basements. Whatever the reason, I love it. These RA103 based Dumont TVs are a favorite of mine too. I restored a Doghouse Chatham to like new condition right down to completely stripping the cabinet and replacing decals etc. There's more evidence of the craze...the fact that decal kits for these old TVs and radios are readily available. Amazing.

I started on the vintage TV thing 55 years ago this year with the late 1940's RCA. I suppose what amazes me most is in 2024 there appear to be more olds becoming available than I recal seeing 40 to 50 years ago.

I would take time travelling through the US North East and I saw very little. Now they seem to be jumping at me.

I don't know what others think.

Nice catches! I especially like the Dumont. But the Emerson is nice too!

My pride and joy!

But seriously, I'll be back on the alignment tonight. I still don't know what resistance pot I'm supposed to use. I'll double check the service data and see what I can find

https://imagizer.imageshack.com/v2/1024x768q70/923/oyldH0.jpg

It is 250K

I do have a 500K rheostat I pulled out of a parts chassis. Would that be useable?

yeah a 500k should do. If it is has an audio taper, set the control mid way and connect the wires to the side with the lowest resistance to center.

The isolation transformer won't help.

Look at it this way: you want to differentially measure a small dc voltage that is not referenced to the chassis ground. A three pronged plug on your VTVM, one os hot, one is neutral and the round pin is case ground. The metal case is grounded via the third pin to protect against you getting a shock if the case is not at ground potential.

.

I know this is a settled matter, but there's one thing I find odd. Your assumption that an isolation transformer will pass it's plugs ground through to its outlet and that the VTVM would have a 3 prong cord... While I wouldn't doubt there are ones that do out there somewhere, I've never seen an isolation transformer built that way out of better than half a dozen I've had. Most isolation transformers I've seen don't have 3 prong cords and many that do don't ground the outlet or use a 2 prong outlet.
Likewise the vast majority of VTVMs made are only 2 prong...It wouldn't surprise me if some lab or mil spec units or some last gasp 80s units might have been built with 3 prongs, but that seems like assuming the exception rather than the rule.... Better to assume the rule and warn to check for the exception in most cases.

What I think I’ll do is wait for the 250K pot that’s coming tomorrow. I took a 6SN7 that has shorts and broke it up and cleaned out the base and pins. I stripped out 2 wires long enough that I could solder them in pins 2 and 5. When the pot comes, I’ll attach it to the wires and mount it on or in, space permitting, the socket. I’ll then have a dedicated tool to align RCA sets with this circuitry.

Thanks for your thoughts on this Tom. I don’t know enough about my isolation transformer to say anything about its ground protections but all of the VTVMs I’ve used have had nonpolarized 2 prong plugs. They’ve all been from the 1950s.

Thanks for your thoughts on this Tom. I don’t know enough about my isolation transformer to say anything about its ground protections but all of the VTVMs I’ve used have had nonpolarized 2 prong plugs. They’ve all been from the 1950s.

When you've had an old isolation transformer developed a primary to secondary short (which also acted as a step up winding) that you accidentally found with your bodys internal volt meter or a persistent ground loop in an agile modulator or ever got zapped connecting a 50s stereo component to a 80s stereo component with a grounded cord you start to learn to check exactly how much your gear is grounded or isolated as well as whether it's hot from line to chassis "safety"/RF line filters despite having a power transformer... Mistakes can be powerful lessons/impetus to learn and check things.

It is important to check grounding between any devices you interconnect even if they're designed to be internally isolated as that can fail. I often measure voltage between devices with my battery powered DMM to prevent sparks flying on interconnection.

BTW metal cone CRTs aren't terrible to handle if you work smart. Always discharge the HV with a HV meter (to prevent dielectric bounce back in the caps) and get a glass test CRT (most metal cone sets a all glass 5AXP4 is the right one) so you can make it run well with the test tube, then at the end reinstall the metal and do width, height, linearity, centering and focus touchups.

I appreciate the effort to keep me safe. Penthode knows what a novice I am and doesn’t want me to get hurt and with good reason. Very appreciative of that.

I know this is a settled matter, but there's one thing I find odd. Your assumption that an isolation transformer will pass it's plugs ground through to its outlet and that the VTVM would have a 3 prong cord... While I wouldn't doubt there are ones that do out there somewhere, I've never seen an isolation transformer built that way out of better than half a dozen I've had. Most isolation transformers I've seen don't have 3 prong cords and many that do don't ground the outlet or use a 2 prong outlet.
Likewise the vast majority of VTVMs made are only 2 prong...It wouldn't surprise me if some lab or mil spec units or some last gasp 80s units might have been built with 3 prongs, but that seems like assuming the exception rather than the rule.... Better to assume the rule and warn to check for the exception in most cases.

You unfortunately misinterpreted what I said. Look at the instructions in manual for adjusting traps. I said the isolation transformer will not prevent the measurement from being a shock hazard.

And my Heathkit VTVM I bought new in 1971 was provided with a power plug third prong or ground. My three earlier VTVMs (two RCA's and a 1950 Heath) did not have the ground connection but my later Heathkit one did.

I only had to emphasize that the dangerous measurement using a VTVM with a metal case at 120 volts B minus potential can cause quite a jolt and one must be aware.

You unfortunately misinterpreted what I said. Look at the instructions in manual for adjusting traps. I said the isolation transformer will not prevent the measurement from being a shock hazard.

And my Heathkit VTVM I bought new in 1971 was provided with a power plug third prong or ground. My three earlier VTVMs (two RCA's and a 1950 Heath) did not have the ground connection but my later Heathkit one did.

I only had to emphasize that the dangerous measurement using a VTVM with a metal case at 120 volts B minus potential can cause quite a jolt and one must be aware.

...and I appreciate that very much!

Why use an ancient VTVM? A modern multimeter has about the same input resistance (usually 10megohm) and is not grounded :scratch2:

jr

Why use an ancient VTVM? A modern multimeter has about the same input resistance (usually 10megohm) and is not grounded :scratch2:

jr

Or if you prefer an analog meter there's any number of FET input VOM meters available that run on batteries. But they are all good to have. :yes:

I have a decent DMM. Probably use that as Penthode suggested about 100 posts ago! It’s accurate enough

Look at the instructions in manual for adjusting traps.

I don't have time to read any manual.... I'm very close to ghosting videokarma for the next few months. Dieseljeep died back in January. I bought up most of his monochrome sets and a few color ones that his family didn't send to the dump. I've got borderline too many projects to complete before winter and reorganize.

I don't have time to read any manual.... I'm very close to ghosting videokarma for the next few months. Dieseljeep died back in January. I bought up most of his monochrome sets and a few color ones that his family didn't send to the dump. I've got borderline too many projects to complete before winter and reorganize.

I understand. I only wish to point out the pitfalls of aligning this particular chassis. Done right the picture and sound is amazing. Done poorly, the picture is difficult to even watch. I have done a number of these ones and can help prevent the pitfalls. That is all.

And I thank you for that. Probably be Thursday before I can get back on this. Busy week but I’ll post as I move along. Thanks to everyone for their guidance and suggestions

Close enough to continue?

https://imagizer.imageshack.com/v2/1024x768q70/924/m318dO.jpg

https://imagizer.imageshack.com/v2/1024x768q70/924/3x65wp.jpg

Cool. I always wanted to get around to putting the pot in an octal socket. And you did it!

Now on to the trap alignment. You need an analog metering device because you are tuning to a minimum. I have very gotten around to getting a digital analog display device because I had the VTVM and it does the job well. You just have to be careful.

Ok so that’s close enough to -4.5v DC?

Ok so that’s close enough to -4.5v DC?

Lol. 4.0 to 5.0 would be okay. It is because as the age changes the bias, the stagger tuned stages response can change. For the traps, the bias is set and you must be careful not to overload the amplifiers as you could get a false null.

Wow, I just read through the adjustment of the traps and there's lots to do! I'm sorta' excited about finally, after a staggering, meandering start, getting somewhere. I've hardly done anything to the alignment and the picture resolution with a multi-burst signal is pretty good.

...and this is where my foundations get a bit thin. What are these "traps" for and why are they called traps? I think, from what I've done and read, they are basically filters that remove unwanted noise from the signal, shunting noise to ground? The ten different megacycle signals from the signal generator fed into the converter grid where the voltage across the resistor is adjusted to a minimum...are those the frequencies we want to pass through the traps with the noise filtered out? Is that the purpose of this set of adjustments? I'm certain my description is devoid of correct terms and electronics specific language but, best I can do!!!

...and this is where my foundations get a bit thin. What are these "traps" for and why are they called traps? I think, from what I've done and read, they are basically filters that remove unwanted noise from the signal, shunting noise to ground? The ten different megacycle signals from the signal generator fed into the converter grid where the voltage across the resistor is adjusted to a minimum...are those the frequencies we want to pass through the traps with the noise filtered out? Is that the purpose of this set of adjustments? I'm certain my description is devoid of correct terms and electronics specific language but, best I can do!!!

The traps are to remove or suppress undesired signals. They essentially suck out or remove certain frequencies.There are three pairs of traps: two lower adjacent video carrier traps, two lower adjacent sound carrier traps and two in band sound carrier traps. The adjacent channel traps were to supress interference from adjacent channels eg if you wish to watch channel 9, the traps will suppress channel 10 video and channel 8 sound if present.

The adjacent channel traps are less important today.But it is important that the traps are correctly set as they will affect the overall video and audio performance of the set. Note the heavy suppression of the 21.25MHz sound carrier allows the video bandwidth to reach the full 4 MHz wide response. Remember most sets of the 1950's bandwdth extended only to 2.5 MHz to around 3 MHz, so this set can produce a much better resolved picture than most other sets.

History; When this set first appeared in 1948, it was when the FCC imposed the channel construction freeze. In 1948 was the first cyclical sun spot peak since television began. The effect was to cause interference between TV stations between cities due to the FCC based upon only line of sight planning. The sun spot peak showed that the signals could travel considerably further than the horizon. Hence in this set design to help mitigate interfence, thorough adjacent channel trapping or suppression was added.

Between 1948-1952, TV stations construction was halted while the industry explored a solution which ultimately resulted in UHF channels 14 to 83 being approved by the FCC in 1952.

A sidenote: I have a model 8T243 (same chassis) and used it for DXing (fishing for distant stations) during the sunspot peak in 1972. I was then able to receive from Toronto Canada, KCMO TV channel 5 Kansas City MO and WPTV channel 5 West Palm Beach Florida. Channel 5 was unallocated in the Southern Ontario Canada/ Western NY region but a strong adjacent channel 6 (CBLT Toronto) prevented all other sets from seeing the channel 5. (After 1952, the adjacent channel suppression in the design was a lot less because of the opening of the UHF band). The set was brilliant for DXing (long distance stations). I last used the same set for DXing in 2009 to view the 'night light' few remaining analog TV stations across the US. I was living in southern Illinois at the time and in 2009 on this set via a 50 foot outside antenna received stations in Phoenix AZ, Albuquerque NM, Denver CO, Regina Saskatchewan, Fredericton New Brunswick, Boston Mass, West Palm Beach FL and Monterrey Mexico. All from the same antenna! So this set was terrific for DXing because of those the traps!

I your case, the most inportant traps to be spot on are the 27.25MHz (lower adjacent sound) and the 21.25MHz sound trap as they especially affect the overall video response. The 19.75MHz trap adjust is only important to ensure it does not tune into the video and audio pass bands as they could distort the response.

Wow…fantastic information and facinating story about the sunspot storm in 1972.

Goodness I think I’m starting to understand some of this! The 21.25 and 27.25 suppression in the video if by the traps thereby expands the video bandwidth?

Goodness I think I’m starting to understand some of this! The 21.25 and 27.25 suppression in the video if by the traps thereby expands the video bandwidth?

The importance of setting the 27.25MHz traps is to help ensure the video carrier is at about 45% on the Nyquist slope. The 21.25MHz traps provide the sharp attenuation below 22.1MHz to allow a wider video bandwidth without the sound interfering with the video. If the 21.25MHz traps are misaligned, you may see a sound carrier beat with the video carrier which is a fine pattern interference. Also the first 21.25MHz trap is the sound take off point for the sound IF amplifier.

And the name “a trap”… does that refer to the trap coil filtering out that one frequency?

And the name “a trap”… does that refer to the trap coil filtering out that one frequency?

You got it!

Yep. It's just a coil and cap in parallel. Traps the resonant frequency.

Does it matter what side of R119 I connect the VTVM? And signal strength on the generator? Cant find that, just where to inject it

I'm pretty certain this is R119 but I'm getting voltage that's pegging the VTVM when I use the suggested 3 volt scale (I'm using the 5V because my VTVM has 1.5V and 5V scale ranges). I was on the other side of the resistor than in this photo when I got that but I'm hesitant to go further. The pot is adjusted for -4.5V DC at the intersection of R135 and R136 on my DMM

https://imagizer.imageshack.com/v2/1024x768q70/922/ild9qv.jpg

I see only one clip lead on the load resistor. Where is the other lead? Is that lead to the VTVM?

Read the instructions. It says you connect the VTVM ACROSS R119. The reason the meter is pegging is because you are measuring the -120vdc B supply!

Going back to the shock hazard thing again: do you understand that the case of the VTVM when you hook it's other "ground" lead to the other end of the resistor, the case of the VTVM will be at -120vdc with respect to the chassis?

Wait...connect the VTVM "ACROSS" R119? Does that mean DC probe on one side of R119 and ground clip on the other side of R119?

Yep, you have it. Just be careful not to touch the case of the VTVM when touching the chassis.

Yep, you have it. Just be careful not to touch the case of the VTVM when touching the chassis.

Yes...got up to step 16. A couple of questions before I proceed. I may need to go back and make some changes.

Where do I set the brightness and contrast controls? As I was starting with the potentiometer adjustment, I had a bright horizontal line which I suspected so I turned the brightness down. As I got further along, the line returned even with minimal brightness. I don't want to burn the tube so I adjusted the contrast to get rid of the line. All of this changed the -4.5V setting so I tweaked that a bit but now that I'm thinking about it, the appearance and disappearance of the line is due to the frequency changes I was feeding in?

I don't know. I guess what I need to know is where to set the brightness and contrast from the beginning and what to do if I see voltage on the pot controlled monitoring spot varying from -4.5V?

Just set the brightness and contrast to minimum. Ensure there is no CRT beam current. That is all.

The -4.5v is only an approximate. The important thing will be you seeing the dip on the meter as you adjust the traps for minimum.

Just set the brightness and contrast to minimum. Ensure there is no CRT beam current. That is all.

The -4.5v is only an approximate. The important thing will be you seeing the dip on the meter as you adjust the traps for minimum.

OK thank you so much! This is actually fun tonight and not the agonies of some other hurdles with this thing. I think I'll go back to the start and just double check up through step 15. Then I'll move on. Could have not have gotten here without everyone's help and especially your guidance and generosity with your time. I've learned a lot through this process so far. Got a way to go with this TV and adjustments so don't go anywhere yet!!!!!!

No problem. There are still some challenges but you are making good progress.

I went back to the very beginning to work my way through and I ran into an issue with one of the trap adjustments. For all of the traps, I could stay on either the 1.5 or 5 volt setting on the VTVM and tune the slug for minimum voltage. I’m not with the TV right now so I can’t relay specifics but after cruising through 3-4 slugs, I ran into one where I had to up the VTVM scale to 50V DC to find a range where I could adjust for a minimum. That’s probably indicative of an issue wouldn’t you say?

I went back to the very beginning to work my way through and I ran into an issue with one of the trap adjustments. For all of the traps, I could stay on either the 1.5 or 5 volt setting on the VTVM and tune the slug for minimum voltage. I’m not with the TV right now so I can’t relay specifics but after cruising through 3-4 slugs, I ran into one where I had to up the VTVM scale to 50V DC to find a range where I could adjust for a minimum. That’s probably indicative of an issue wouldn’t you say?

The issue which happens with this chassis is that if the circuits are not stagger tuned, there is the chance of feedback. The loss of proper stagger tuning comes when someone adjusts a circuit and are not sure what they are doing. I have received sets like this. And the cure is straight forward especially with the precise equipment you are now using.

I will wait for more details so I can be sure what is going on.

Weekend got busy. Be back on it Monday and Tuesday during the day. Thanks so much!

I went through all of the steps through the video IF and trap adjustments that are done from the top of the chassis (step 11 on the alignment table). I was able to do all of the minimum voltage adjustments with the VTVM on the 1.5V scale. The signal is being fed into V102 pin 1 at 300mv through a 1500pF ceramic capacitor.

The max/min swings on the VTVM while adjusting the slugs were pretty minimal. That didn't exactly fill me with confidence! Could my input signal strength be too low at 300mV?

I have not encountered the problem described earlier where I had to increase the VTVM DC range to 50V. I must have seen that while going through the adjustments on the bottom of the chassis for maximum deflection on the meter.

Well...in typical me fashion, I didn't encounter the need for the voltage range adjustment on the VTVM all the way through step 15 on the alignment table this time through. I was able to do all of them on the 1.5V scale. I had a difficult time turning the bottom adjustment for step 15, the bottom of T102. I didn't want to push it and break the coil/slug. I'm wondering if I should check the video and sound quality and if the sound and picture are in sync when a signal is sent in from my VA62 and I tune in the set channel for the RF input? I'm going to need help with steps 16 and 17 anyway. Pretty complicated for this numbskull.

Checked the picture quality with the signal generator multiburst signal. I really don't know that much about this pattern except to read the vertical bars for resolution. From the right side, there's actually some vertical lines I can distinguish in the last 2 bars but I don't know if that's actual video. The third bar from the right has no resolved lines but from there all the way to the last bar on the left, there's good clean resolution. Sound and video still not aligning no matter how much the fine tuning is adjusted.

Note: Not signal generator...I meant video generator Sencore VA 62

OK...not in any particular order...

1. How am I supposed to sweep the signal? The 2 frequencies, 22.05 and 24.75 are the peaks of the sweep in Figure 15 (and Fig 28 photo) and should be set in the marker generator correct?

2. Am I sweeping with a central frequency of 25mc a symmetrical sweep of 10mc? Is that what's required by the instructions "Sweeping 20-30mc" under the Sweep Gen Freq Mc column in the alignment table or am I reading that completely wrong?

3. Set bias -2V. Does that mean adjust the 250k pot for a reading of -2V at the R135-R136 test point as before?

4. Now for the biggie...shunt a 330 ohm resistor across the primaries of T-102, 103, 104 and 106. Does that mean connect 330 ohm resistors between the transformer tabs of the primary coils of all 4 of the transformers? How, solder them in? Please say no! :tears::tears::tears:

Whoa! You are jumping too fast here and making wrong assumptions.

The trap nulls are pretty obvious and should be more dramatic. You should aim to getting about two to four volts across the detector load on the VTVM. The trap is nulling out. If so you increase the signal level until you see a good null. Did you do all the traps properly? It is very important before you move on.

No I didn't think so. I was injecting the frequencies at around 200mV into V2 Pin1 through the 1500pF cap. I was not getting swings anything like 1.0-2.0 volts DC. Is 200mV not strong enough???

Moving old ferrite slugs is fought with danger. The Canadian built RCA is is better than the US version as far as the transformer construction is concerned because in Canada they used brass threaded extensions to the ferrite cores. The US sets used slots in the cores themselves.

The adjustments should not need to be much the the stagger tuned cores (bottom ones) unless in the last 75 years someone has been there before.

For reluctant ones, I like to direct a heat gun with an aiming nozzle at the hole to warm it a bit. NEVER FORCE A RELUCTANT CORE. They are very brittle and easily snapped and are a devil to remove and replace!

No I didn't think so. I was injecting the frequencies at around 200mV into V2 Pin1 through the 1500pF cap. I was not getting swings anything like 1.0-2.0 volts DC. Is 200mV not strong enough???

200mV is way too low. I would go back and increase the RF signal applied.

Well...in typical me fashion, I didn't encounter the need for the voltage range adjustment on the VTVM all the way through step 15 on the alignment table this time through. I was able to do all of them on the 1.5V scale. I had a difficult time turning the bottom adjustment for step 15, the bottom of T102. I didn't want to push it and break the coil/slug. I'm wondering if I should check the video and sound quality and if the sound and picture are in sync when a signal is sent in from my VA62 and I tune in the set channel for the RF input? I'm going to need help with steps 16 and 17 anyway. Pretty complicated for this numbskull.

Way too premature. You only check the picture and sound quality when you are finished.

Checked the picture quality with the signal generator multiburst signal. I really don't know that much about this pattern except to read the vertical bars for resolution. From the right side, there's actually some vertical lines I can distinguish in the last 2 bars but I don't know if that's actual video. The third bar from the right has no resolved lines but from there all the way to the last bar on the left, there's good clean resolution. Sound and video still not aligning no matter how much the fine tuning is adjusted.

Note: Not signal generator...I meant video generator Sencore VA 62

As I said this is all too premature.

Moving old ferrite slugs is fought with danger. The Canadian built RCA is is better than the US version as far as the transformer construction is concerned because in Canada they used brass threaded extensions to the ferrite cores. The US sets used slots in the cores themselves.

The adjustments should not need to be much the the stagger tuned cores (bottom ones) unless in the last 75 years someone has been there before.

For reluctant ones, I like to direct a heat gun with an aiming nozzle at the hole to warm it a bit. NEVER FORCE A RELUCTANT CORE. They are very brittle and easily snapped and are a devil to remove and replace!

Got it. I think my VTVM is a bit wonky. One more question...the channel selector is set between channels 2 and 13 but that's not a firm detent correct? I just have it between the two channels.

200mV is way too low. I would go back and increase the RF signal applied.

What would you suggest...600mV?

OK...not in any particular order...

1. How am I supposed to sweep the signal? The 2 frequencies, 22.05 and 24.75 are the peaks of the sweep in Figure 15 (and Fig 28 photo) and should be set in the marker generator correct?

2. Am I sweeping with a central frequency of 25mc a symmetrical sweep of 10mc? Is that what's required by the instructions "Sweeping 20-30mc" under the Sweep Gen Freq Mc column in the alignment table or am I reading that completely wrong?

3. Set bias -2V. Does that mean adjust the 250k pot for a reading of -2V at the R135-R136 test point as before?

4. Now for the biggie...shunt a 330 ohm resistor across the primaries of T-102, 103, 104 and 106. Does that mean connect 330 ohm resistors between the transformer tabs of the primary coils of all 4 of the transformers? How, solder them in? Please say no! :tears::tears::tears:

Here are my answers:

1. Yes this is the over coupled transformer link between the tuner and 1st IF stage. They advise you separately check and you are correct the peaks are 22.05MHz and 24.75MHz. Set the sweep generator to roughly 24MHz and set the sweep width to symetrical and widest seting.

2. No. What the instructions is saying is to roughly sweep to cover the bandwidth you are aligning. You want toe see the peaks and the srts of the resonse curve.

3. Yes that is it. Just be aware that you can overload the amplifier. Adjust the input RF sweep signal so that you get about 3 vDC at the detector.

4. I bought a bunch of 330ohm 1/4 w resistors and soldered small croc clips to either end. I then attached the croc clips to the terminals if the IF transformers. The reason for doing this is of course to remove the tuning of each IF stage so you can see the overcoupled transformer link performance.

What would you suggest...600mV?

600mV where? I am talking about looking at the voltage at the detector, You increase the input until you see roughly 2 or 3 volts at the detector load.

OK thanks. Going through the traps again. My probe clip connection was not solid. Seeing much more clear responses with changes in the traps. Meeting at 3p!!! Working hard here!!!

600mV where? I am talking about looking at the voltage at the detector, You increase the input until you see roughly 2 or 3 volts at the detector load.
Wait...now I'm confused. I thought you were talking about increasing the strength of the RF output frequencies from the 8601. There's a lot of changes to the -4.5V voltage I set with the pot if I vary the output voltage from the 8601. Should I not even monitor that -4.5V?

Wait...now I'm confused. I thought you were talking about increasing the strength of the RF output frequencies from the 8601. There's a lot of changes to the -4.5V voltage I set with the pot if I vary the output voltage from the 8601. Should I not even monitor that -4.5V?

Just set as per instructions and leave it. What do you mean lot of changes?

Just set as per instructions and leave it. What do you mean lot of changes?

Never mind...I'm looking for too many things I think might be potential issues with just a rudimentary understanding of what I'm doing. I went through all of the traps again and saw good min/max on the VTVM. The minimum and maximum adjustments came with real swings on the meter and not subtle ones. There are a couple of things bothering me. When I tried to peak the secondary on T-106, I didn't see a peak until the adjustment was about half an inch screwed out of the bottom. I've done this about 5-6 times on this adjustment. I've run the slug from all the way in to about an inch of threads out on the screw. Where I have it now is the only peak on this secondary throughout the entire range of possible settings. The frequency fed into the converter grid is 22.5mc for this adjustment. I understand you said these shouldn't need to be moved too much but this one did. It's more than a bit possible I moved it when I was working on this over the past 2 weeks.

Mu other concern is the stiffness on the final peaking slug on the secondary of T-102 at 22.9mc fed in. It was really stiff so I didn't push it. Maybe I will try some heat as you suggested. I have a hot air gun in my soldering station that has a variety of tips so I can direct the heat exactly where I want it.

I'm getting confused just trying to follow all this. :(
As Penthode said, the -4.5 is set and forget, set at the start, and don't touch, or it will throw all things off, it's meant to suppress some circuits while you do the alignment, you do not need to monitor it.

I'm getting confused just trying to follow all this. :(
As Penthode said, the -4.5 is set and forget, set at the start, and don't touch, or it will throw all things off, it's meant to suppress some circuits while you do the alignment, you do not need to monitor it.

Setting it to -4.5v is simply fixing the AGC to a voltage close to normal operating voltage. The reason is that the IF response changes very slightly as you change the bias. Consider that the IF strip comprise of staggered stages employing the same vacuum tubes which have slightly different characteristics in the course of manufacture. In this world, nothing is perfect and engineering is always a practical compromise.

So the -4.5v is not an absolute. Is is a rough approximation of where it normally would be under average reception conditions.

(My philosophy: I often muse that in our digital world today, the display layer is what most now look at which is defined by a series of precise digital words which if is not corrupted in reception provides a closer to perfect ideal. Not so in the world of analog systems and television where the display layer doubles as the transport layer and is subject to vagaries like this.)

I'm getting confused just trying to follow all this. :(
As Penthode said, the -4.5 is set and forget, set at the start, and don't touch, or it will throw all things off, it's meant to suppress some circuits while you do the alignment, you do not need to monitor it.

Hey...me too! I got it about the "set and forget it" -4.5 volts. I'm not sure how Penthode would like to go forward. These settings are critical to the quality of everything going forward and I've gotta get it right. Maybe I'll post what's going on with pictures of each step and look for input from everyone and a consensus all is good before I go on to the next trap adjustment.

I've ordered some mini alligator clips so I can solder up 4-5 330 ohm, easy on/easy off shunts for the transformers in the last 2 steps in the alignment table.

Setting it to -4.5v is simply fixing the AGC to a voltage close to normal operating voltage. The reason is that the IF response changes slightly as you change the bias. So the -4.5v is not an absolute. Is is a rough aproximation of where it normally would be under average reception conditions.

That's what I thought, I did something like that with my Hoffman, the clip lead fell off on try #2, and I had to start all over again!:tears:
#3 worked pretty well!

Now you are making me confused.

The pot is adjusted for setting the -4.5v which is the AGC voltage measured at the junction of R135 and R136 wrt ground.

The RF CW signal is detected or rectified by the 2nd detector. You vary the 8601a signal until you get roughly 2 to 3 volts ACROSS the detector load resistor R119. The -4.5v should not be changing much: how much is it changing?

Got it. I think my VTVM is a bit wonky. One more question...the channel selector is set between channels 2 and 13 but that's not a firm detent correct? I just have it between the two channels.

That is correct. There is no detent.

Historical note: This, the KRK5 RCA tuner replaced the KRK2 tuner used in RCA sets from 1946-48. The KRK2 included Channel 1 and the KRK5 in 1948 was the first RCA tuner to drop channel 1. The blank space is where channel 1 would have gone.

with regards to the core positioning for maximum. You said the core was unscrewed to get the peak. Unscrewing the core reduces inductance which means you are tuning it higher in frequency. What I think you have done is tune it to the same frequency as another stage and it has introduced oscillation! I mentioned the danger earlier of it breaking into oscillation. I suggest you must fix this before adjusting the traps!

Put the core back close to the original position. The circuit tunes broadly and you should detect a smaller peak near the original position. Also if you do get into a state of oscillation and cannot get out of it, what you do is increase the AGC voltage until the oscillation ceases and try increasing the 8601a input until you see the signal.

Certainly if you are having to adjust any opf the circuits that far away, you are doing something wrong. Becareful and stop and think and ask before making assumptions.

Now you are making me confused.

The pot is adjusted for setting the -4.5v which is the AGC voltage measured at the junction of R135 and R136 wrt ground.

The RF CW signal is detected or rectified by the 2nd detector. You vary the 8601a signal until you get roughly 2 to 3 volts ACROSS the detector load resistor R119. The -4.5v should not be changing much: how much is it changing?

It's not...I was varying the output RF voltage way too high messing with it when I had a bad VTVM lead connection. With the latest min/max adjustments it didn't vary much at all

with regards to the core positioning for maximum. You said the core was unscrewed to get the peak. Unscrewing the core reduces inductance which means you are tuning it higher in frequency. What I think you have done is tune it to the same frequency as another stage and it has introduced oscillation! I mentioned the danger earlier of it breaking into oscillation. I suggest you must fix this before adjusting the traps!

Put the core back close to the original position. The circuit tunes broadly and you should detect a smaller peak near the original position. Also if you do get into a state of oscillation and cannot get out of it, what you do is increase the AGC voltage until the oscillation ceases and try increasing the 8601a input until you see the signal.

Certainly if you are having to adjust any opf the circuits that far away, you are doing something wrong. Becareful and stop and think and ask before making assumptions.

OK I will go back and turn the core back in on T-106 and look for the smaller peak.

Oh darn darn darn darn darn...I think I may have done something wrong! Now this is how inexperienced and electrostupid I am...but it's good because I'm making mistakes I'm learning from...

I was not paying attention to the VTVM DC voltage position...positive or negative. Obviously, if it was set to DC-, the peak is going to be deflection of the meter to the left correct? I can't account for the position when I did the min/max adjustments so it's back to step 6 once again!!!!!!! Besides getting valuable lessons, I sure am learning this particular chassis and the audio and video circuits!

Maximum is deflection to the right and minimum is the dip to the left.

The problem here is the careful staggered tuning in order to get the full 4MHz bandwidth. There is a lot of gain in the four stages. You can assume unless someone before has tinkered with it, the stages were close to being correct.

So let's go back. Make sure it is not oscillating. To confirm it is not oscillating, switch the HP8601a off and ensure there is no voltage across the 2nd detector load. By no voltage, I mean less than 100mV. Confirm the traps are correct and then set the preliminary staggered tuning setup prescribed in the manual. The spot frequencies are to get the alignment close before the sweep alignment.

Maximum is deflection to the right and minimum is the dip to the left.

The problem here is the careful staggered tuning in order to get the full 4MHz bandwidth. There is a lot of gain in the four stages. You can assume unless someone before has tinkered with it, the stages were close to being correct.

So let's go back. Make sure it is not oscillating. To confirm it is not oscillating, switch the HP8601a off and ensure there is no voltage across the 2nd detector load. By no voltage, I mean less than 100mV. Confirm the traps are correct and then set the preliminary staggered tuning setup prescribed in the manual. The spot frequencies are to get the alignment close before the sweep alignment.

Ok I will do that. Gotta shut it down tonight. Be back on it tomorrow evening

This snip is from a different RCA model alignment set of instructions but the chassis has the same traps and the same frequencies. There's something in here I don't understand...
https://imagizer.imageshack.com/v2/1024x768q70/923/oCf14u.jpg

I see the warning about getting false, resonant peaks and nulls when "running the cores completely through" . I don't understand the next statement..."The correct position is with the cores in the outside ends of the coils". What do they mean by outside ends?

It means positioned near the top or bottom rather than the center of the coil.
In other words, start with the coil mistuned by having the core too near the end and move towards the center to get the correct tuning, rather than starting with the core near the center and turning to go towards the end.

https://live.staticflickr.com/65535/54004905900_b372378f94_z.jpg

Note in both cases the upper and lower coils are each tuned correctly. The only difference is the amount of coupling. Too much coupling will produce a wide double-humped response with low center frequency response.

https://live.staticflickr.com/65535/54004905900_b372378f94_z.jpg

Note in both cases the upper and lower coils are each tuned correctly. The only difference is the amount of coupling. Too much coupling will produce a wide double-humped response with low center frequency response.

Wow...thank you so much. Resonance...harmonics etc...these concepts have always been the most challenging things for me. I can understand a vibration stimulating something else at rest to vibrate but at the same frequency. I don't entirely understand the production of other frequencies from the primary one.

So by coupling here you mean frequency or vibrational coupling...one coil and slug stimulated electrically transferring this frequency based energy to an adjacent coil? These traps are tuned to eliminate specific frequencies from the signal circuit resulting in a broader bandwidth. At least that's my understanding from an earlier part of this thread. How does this primary/secondary tuned pair do that? I have an idea as to how but I'm not very eager to put it out there! :no::no::no::no:

It's a magic spell, and you are a mystical witch casting a spell on the set, mixing all the ingredients in your cauldron one at a time VERY carefully, get one wrong or out of order, it's all messed up, and you have to start ALL OVER AGAIN! :D :yes:

I also wish to point out the coil you were earlier adjust from the bottom was not a trap but a stagger tuned stage. Take heed of the attached warning from the manual. This unfortunately happens when one begins making changes without carefully reasoning through.

So for the traps, you are to find the null with the core on the outer most postion. The stagger tuned stages should be in the relative position you started with. If it falls into oscillation, as I am sure others have had on the model, then tuning each stage to the correct physical (original) position should eliminate the oscillation. I have only had to resort to increasing the bias to fix stubborn cases and never having to shunt stages. But if you are not careful you may have to resort to that in order to get back where you started.

I’m trying. I knew I would cause more problems than I solved once I started messing with this.

Is there something I should know about a staggered tuned IF? I thought an IF was just a gain increasing series of steps through vacuum tubes and stages. Is staggered tuned different from a standard IF sound or video IF?

As I mentioned early on, this is one of the most challenging sets to align even for the most seasoned techs who have done alignments, so it's understandable you are having trouble, perhaps you can sharpen your teeth on a newer less complicated set first?

Wow...thank you so much. Resonance...harmonics etc...these concepts have always been the most challenging things for me. I can understand a vibration stimulating something else at rest to vibrate but at the same frequency. I don't entirely understand the production of other frequencies from the primary one.

So by coupling here you mean frequency or vibrational coupling...one coil and slug stimulated electrically transferring this frequency based energy to an adjacent coil? These traps are tuned to eliminate specific frequencies from the signal circuit resulting in a broader bandwidth. At least that's my understanding from an earlier part of this thread. How does this primary/secondary tuned pair do that? I have an idea as to how but I'm not very eager to put it out there! :no::no::no::no:

The coils between IF stages are coupling the output of one stage to the input of the next. But coupled coils can also be used in a trap circuit where one of the coils connects to a circuit that absorbs energy at the trap frequency instead of passing it to a next stage. And sometimes, the coupled coil is both a sound takeoff that sends the sound signal to the audio IF and and also a sound trap in the video path because it sends the sound signal out of the video path and to the sound IF.

Another thing, we are discussing basically linear filter circuits here, which means they (ideally) do not generate harmonics of the incoming signal, but respond with different amplitude to the different frquencies that are present in the incoming signal. This difference in amplitude at different frequencies is seen as the shape of the IF alignment sweep curve.

"Standard IF" is not a useful designation.
The "opposite" of staggered tuning is synchronous tuning. Both of these generally can apply to any IF where each stage has a single resonant circuit (coil and capacitor).
Synchronous tuing means every stage is tuned to the same frequency, and the overall response has the single peak frequency with a bandwidth narrower than any one stage. With stagger tuning, the peaks of the individual stages are different, so one stage may have maximum response at center, while others have maximum at higher or lower frequency. Stagger tuning produces less gain at the center freuency, but boosts the gain somewhat at higher and lower frequency, giving a wider bandwidth.

Then there are double-tuned stages, as illustrated above. A double-tuned amplifier has two tuned circuits between stages that are coupled (usually magnetically, but could be with a capacitor). Even though each tuned circuit is (usually) tuned to the same frequency individually, when they are coupled the response bandwidth becomes broader, and if the coupling is strong, will actually develope a double-peaked response, with a dip in the middle.

Fun fact: coupled oscillator theory applies to any sort of coupled resonators including mechanical objects. It is used on those strange dumbell type weights (vibration dampers) you may see on high tension wires, to reduce wind vibrations, and also in "mass dampers" in some tall skyscrapers to reduce wind sway.

This is an interesting discussion! With stagger tuning you are not adjusting the four stages to one single frequency like in the FM stages or in an AM Radio. The stages are tuned to different frequencies or stagger tuned.

Simply put, stagger tuning is to stagger the frequencies each stage is tuned to. This is to provide the wideband needed to accommodate the wide bandwith video signal.

The stages are tuned to different frequencies so that the combination of the whole provides the over 4MHz bandwidth required.

Another point to understand and appreciate is the use of vestigial transmission for the video. For standard amplitude modulation (AM radio broadcast for example) both sidebands are transmitted. For television requiring 4MHz for the signal would require a 8MHz wide channel for both the AM sidebands. In the late 1930's it was discovered that if most of one of the sidebands was removed, a full resolution video could be delivered at the expense of slightly worsening the signal to noise performance of the transmission. So Vestigial Sideband is the sending only a "vestige" or portion of one of the sidebands.

How this relates to your alignment is the importance of placing the video carrier at exactly the 45% point of what is termed the "Nyquist Slope". Setting the carrier too high on the slope will emphasize the lower video frequencies in relation to the higher video frequencies. The higher video frequencies contain the fine detail in the displayed video. So improper carrier placement too high on the curve will make the picture less sharp and fuzzy. Conversely, the carrier too low on the curve will make the picture too sharp and edgy and make the picture noisy. Watching NTSC color signals on with the carrier too low will emphasize the subcarrier dots and destroy the image.

This you have to keep in mind when doing the sweep alignment.

We can discuss more closer to the time. Let's first get back to where we were and establish a baseline from which to begin the stagger tuned alignment.

One other thing. The coupling between the tuner and the first video IF is not stagger tuned or part of the overall stagger tuning in this design. Instead the stage includes an overcoupled transformer link. That is the stage cannot be adjusted to one single frequency. Instead it tunes very broadly.

To align this stage separately, you must follow the instructions and sweep align it before doing an overall sweep alignment.

Thank you everyone. Let me digest this for a bit. Getting a little bit “behind the aircraft” as they say in aviation accident investigations! I need to put all this information together in my head and ask some questions. Standby!

As I mentioned early on, this is one of the most challenging sets to align even for the most seasoned techs who have done alignments, so it's understandable you are having trouble, perhaps you can sharpen your teeth on a newer less complicated set first?

Hard for me to give up on a project even for a short while once I've started. I think I'll learn more not just from the difficulty but also from the engineering chronology of how these RCA TVs were designed, modified and redesigned over the first few years after the war. All that being said, one or two projects are currently on the shelf waiting for an "Ah Ha...That's what's wrong with that one!" moment

Having worked on RCA televisions prior to and after this chassis, you chose the most compluicated early receiver to re-align. You are making progress and have highlighted the pitfalls in the process along the way.

I think you should feel confident once you are through this set you should feel confident attacking any other set.

Having worked on RCA televisions prior to and after this chassis, you chose the most compluicated early receiver to re-align. You are making progress and have highlighted the pitfalls in the process along the way.

I think you should feel confident once you are through this set you should feel confident attacking any other set.

I agree...It's not the first time I've chosen the steepest learning curve in my life and I do intend to stick with it as long as the good will of yourself and all the other contributors to this endeavor continues. Compared to where I was a couple of months ago, I feel like I've come a long way in understanding how these early commercial TVs were designed and how this first generation was subsequently modified. I've also acquired some impressive equipment for the Starship bridge!

Speaking of equipment, I bought a serviced and calibrated new VTVM off eBay from a seller with a long history of electronic sales. To be honest, I don't trust that my present VTVM is giving me accurate information and consistent sensitivity. I'll plug along with it for now but the replacement should be here shortly.

Learning curve just got significantly steeper. I broke the T-103 73572 bottom slug. Looks like the slot sides broke out. How do you curse profusely on VK without being banned? Can't believe it. I've got a couple of 630 parts chassis but they don't have this 21.5/22.0mc trap coil. For the cursing, here's the best I can do :dammit::dammit::dammit::dammit::dammit:

I was warned about this. Crap. I was being gentle but happened anyway. I looked on eBay and the RCA transformer stock at the ETF but no joy.

Dont worry. I expect everyone has been there and done this. If they say the have never had this problem, they are lying!

Fortunately it is easy to remove the coil assemble from the chassis. And unlike many modern components, you can actually take it apart and fix it!

The first thing is to carefully remove it and examine. A few photos posted here will help decide what lies next.

Did the core split? If I recall the core has slots either end and if the top core is removed you should have access to the other slot.

Need to know the extent of the damage so far.

Dont worry. I expect everyone has been there and done this. If they say the have never had this problem, they are lying!

Fortunately it is easy to remove the coil assemble from the chassis. And unlike many modern components, you can actually take it apart and fix it!

The first thing is to carefully remove it and examine. A few photos posted here will help decide what lies next.

Did the core split? If I recall the core has slots either end and if the top core is removed you should have access to the other slot.

Need to know the extent of the damage so far.

OK if I can turn it out from the top I'll do that...gently!

The core did not split and I can see the top of it from the top of the chassis side. Should I unscrew it up and out of the top of the coil or screw it down through the bottom?

I don't want to remove the coil from the chassis if I can help it. I can see the top and bottom of the core. The top of it has a slot, the bottom dies not and there's a little debris I cleaned out from what broke off. Very difficult to photograph but the core is intact...I just have to get it out and screw it in from the bottom

Here is a photo of the bottom with it run all the way down. The only think that broke was the parts of the core on the sides of the slot.

https://imagizer.imageshack.com/v2/1024x768q70/922/hhvtfl.jpg

I always use a hard plastic tool to adjust the cores. Try and refrain from using a metal tip because unless the tip fits snugly, the uneven sape will imose high stress to the brittle slug slot wall. I carved a hard plastic rod to the shape of the slot.

You can see the slot the other end? I would gently try and screw it downward and out. Do not force it if it jams.

If the core only has the slot damaged one end and is otherwise okay, I would simply flip it 180 degreses and put it back and continue the alignment.

correct that, I didn't recall the brass ring obstruction. Remove it from the top seems the only option.

correct that, I didn't recall the brass ring obstruction. Remove it from the top seems the only option.

I agree...slowly turning it out with a plastic flat blade tool.

I cant get it out the top. I can feel the slot starting to go. I looked down into it very gently blew the threads clean and the debris out and I think it's coming up as far as it's going to go without breaking it. So I think I'm back to replacing the coil or getting this core out and finding a substitute. From what you've tald me about this TV, that's probably not going to work.

I have an entire parts chassis out in the garage. It probably still has this coil

I have an entire parts chassis out in the garage. It probably still has this coil

Wow. If you could check and let me know I would so appreciate that. You can email me Bob

I cant get it out the top. I can feel the slot starting to go. I looked down into it very gently blew the threads clean and the debris out and I think it's coming up as far as it's going to go without breaking it. So I think I'm back to replacing the coil or getting this core out and finding a substitute. From what you've tald me about this TV, that's probably not going to work.

That is good that spares are available. But with a bit of judicial manipulation and patience, let us try and remove the core. The worst thing is you simply have to replace the slug.

Have you tried a bit of heat to melt the wax residue?

I have never had to replace one of these transformers. They are fixable.

Were not those donono mica capacitors that was shown in the above pic a source of trouble in these sets?

Funny talking about HP8601a's, I found another one locally on FB Marketplace today. It came from the estate of a local engineer.

There was a whole pile of high end HP and Tektronix test equipment from the 60's thru the 1980's. I wanted only the Tektronix 2710 Spectrum Analyser and the HP8601a and offered C$120. The seller wanted to dispose of the lot which included a second Spectrum Analyser with tracking generator, a few high end older Tektronix scopes, an HP 8640 HF to SHF sweeper generator, a huge pile of Tektronix plug in modules Tek digital multimeter, frequency counter, low frequency function generators, a three foot desk equipment rack scope probes and a nice looking Wavetek Sweeper with marker option. All for C$200.

Maybe I can dispose of the surplus stuff to pay for the HP8601a and the Tek 2710 Spectrum Analyser?

That is good that spares are available. But with a bit of judicial manipulation and patience, let us try and remove the core. The worst thing is you simply have to replace the slug.

Have you tried a bit of heat to melt the wax residue?

I have never had to replace one of these transformers. They are fixable.

If Bob can locate a replacement for me, I’ll try just for the experience.

Were not those donono mica capacitors that was shown in the above pic a source of trouble in these sets?

Good question. I have found one bad but I generally haven't had much trouble with them in these sets. I would be curious if others have.

Good question. I have found one bad but I generally haven't had much trouble with them in these sets. I would be curious if others have.

I believe bandersen mentioned something about them before. yes, namely the 270pf caps.

Yes, I've sometimes needed to replace the 270pF mica caps that couple the IF stages. However, it looks like you are getting a good image so I would not be concerned about them.

I might have a line on a refurbished and calibrated 8601 for a very decent price. PM me if anyone is interested.
I’m going to remove the T-103 trap transformer from the chassis. It’ll be easier to work on and it’s gotta come out anyway if Bob can provide a replacement

So you had no success getting the slug out? What are you using for an alignment tool? It is important you use only the correct tools.

I should have said on the outset of this adventure, normally the alignent is fairly close. The sound IF is narower bandwidth and is best gone over more concisely. The traps too need a little adjustment but they should be fairly close.

Because the video IF stagger tuned stages are pretty tuved for a broad response, there was really no need to perform the steps to spot align each stage. All that needed to be done was first sweep the overall video IF and only perform a few touch ups to get the response in the manual. I would only resort to deeper investigation if the response is bad and not easily corrected.

When looking at the overall response, and knowing where each of the stagger tuned stages is tuned to, you would look at what part there is a deficiency and adjust only slightly the appropriate stage. For example, the 22.1MHz marker is too low or not in the right place. I would first slightly adjust T103 bottom in combination with T105 bottom to try and make that part of the response correct at that point. Or the video carrier is not at the 45% point, I'd adjust T102 bottom and T104 bottom only slightly to fix it there. Only vey slight ajustments would be necessary. If that fails, then I would shunt each stage with the 330 ohm resistors and check by sweep alignment of the T1/ T101 the overcoupled Tuner to 1st IF link. In every case only a small adjustment while looking at the bsweep and if the adjustment makes it worse to back off and put the adjustment back to where it was before moving somewhere elese to adjust.

Unfortunately the adjustments now appear all over the place. You will need to highlight how much you adjusted to try and undo what you have done.

I repair clocks and watches and fine machinery. I wind and make my own transformers if the originals are damaged. I do not know what experience you have repairing these things. But the core can be removed and I believe a standard hex hole core slug can be used as a replacement.

Small world…I’ve restored dozens of mechanical watches. Disassembled, cleaned in a vintage Elma watch cleaning machine, reassembled with capstone and jewel pivots oiled with 9010…regulated on a time grapher.. I used to do all that! Then I started medication that made my hands tremble just a tiny bit but it was enough. No chance of doing it anymore.

So the strategy the next time would be to do whatever needs to be done preliminarily, like in this case, the sound discriminator response and the sound IF response but at that point, before getting lost in the weeds of going through each step in adjusting traps and IF transformers, just go to the overall IF/RF response curve and see how well it's aligned. If changes need to be made, then individual transformers, coils, traps etc can be individually targeted to make subtle adjustments to firm things up on the overall trace.

If this TV is so screwed up now it's basically unsalvageable, that's fine. Just this learning experience has been so valuable to me I'd do it all over again! Remember, at the beginning of this, I had never seen a response curve for any TV I've ever worked on. It looks like the reason for that was bad and unreliable equipment as much as my inexperience. Where I am and this workbench is are miles more advanced from a couple of months ago!

I'm not giving up yet. I'll get this broken slug out and find a comparable one to replace it with. I want to get the transformer, T-103, out tonight as step one.

So the strategy the next time would be to do whatever needs to be done preliminarily, like in this case, the sound discriminator response and the sound IF response but at that point, before getting lost in the weeds of going through each step in adjusting traps and IF transformers, just go to the overall IF/RF response curve and see how well it's aligned. If changes need to be made, then individual transformers, coils, traps etc can be individually targeted to make subtle adjustments to firm things up on the overall trace.

If this TV is so screwed up now it's basically unsalvageable, that's fine. Just this learning experience has been so valuable to me I'd do it all over again! Remember, at the beginning of this, I had never seen a response curve for any TV I've ever worked on. It looks like the reason for that was bad and unreliable equipment as much as my inexperience. Where I am and this workbench is are miles more advanced from a couple of months ago!

I'm not giving up yet. I'll get this broken slug out and find a comparable one to replace it with. I want to get the transformer, T-103, out tonight as step one.

The set is far from screwed up. I would stick with it as it is a great learning experience. And for me that is what it is all about: learning new things. I smile because once you have mastered this set you should have the experience to work on other stuff like this.

The set is far from screwed up. I would stick with it as it is a great learning experience. And for me that is what it is all about: learning new things. I smile because once you have mastered this set you should have the experience to work on other stuff like this.

Ditto! You have made progress all through this and never reached a state anywhere near "unsalvageable."

The set is far from screwed up. I would stick with it as it is a great learning experience. And for me that is what it is all about: learning new things. I smile because once you have mastered this set you should have the experience to work on other stuff like this.

I know and thanks for the encouraging words. Not sure what to do about broken parts though. These 3 trap units are the same part number...they are just tuned differently.

https://imagizer.imageshack.com/v2/1024x768q70/924/WSdSzc.jpg

Ditto - not even remotely unsalvagable. Heck, you don't even need some of the traps for it to work. There aren't going to be any adjacent channels in your area.
By the way - this is why I don't align most sets and when I do it's often just the sound. Great learning experience none the less.
Yes, these are capable of excellent image resolution but that also requires you to feed it a signal with good bandwidth. Most sources are going to be band limited because of color info. There are ways around this but that's a topic for another thread.

I would beg to differ on one point. The traps especially in this set help shape the overall bandwidth. If you want to achieve the full four megahertz, setting the traps as prescribed accurately is important. And with the HP equipment you can set it as good or beter than before it left the factory.

T103 is a little different: the trap set to 21.25MHz and this trap provides the sound IF take off point.

So providing the center tube is clear, the new slugs should fit.

I do have to admit that I recall over 50 years ago I took apart the T103 in my set for a simiar problem. The Canadian version I have, unlike the US version, uses a brass threaded screw to the ferrite core, similar to the width coil on your set. The bottom threaded clip insert snapped when I tried to adjust it. I had to remove also T103, unsolder the tap wire on the middle othe trap and take pull the black bakelite cover off to access the inside. once apart, I had to unsolder the fine wires to the tabs to pull the coil off and replace the broken clip which was nested at the bottom of the coil in the brass cup.I replaced it with a reshaped spring matching the original shape, I reassembled solder back the tap wire and reinstalled the transformer. The set aligned very well using the equipment I used then (having to set a generator marker frequency interpolated between beating with a crystal harmonic). In those days of a crowded VHF band, I had to ajust slightly the adjacent channel traps using off air signals. Eg. I would receive a weak channel 10 from WHEC Rochester. The fine tuning because it is of a split sound design is for best sound. So the fine tuning on these sets is very precise. Once set for best sound on channel 10, we had strong adjacent channels on CFTO channel 9 Toronto and CHCH channel Hamilton. So to minimize adjacent channel 9 sound in picture, I would touch up slightly the 27.25MHz traps and for CHCH channel 11 video ineterface in channel 10, I would slightly touch up the 19.75MHz traps.

It is with this alignment much later in 2009 I could use the set to DX when living in Southern Illinois. Look at the snapshot of WPTB Channel 2 West Palm Beach Florida received 1500 miles away despite a strong adjacent WSIL channel 3 Carterville Illinois located about 10 miles away. No other set, even much newer sets had the adjacent rejection capability of this RCA chassis!

The two photographs below show on off air channel 8 from KAET Phoenix. The four Megahertz resolution brings out a lot of fine detail. The second photo is a weak WPTB channel 2 received 1500miles on this set witha standard antenna atop a 50 foot mast direct to the receiver tuner with no preamp.

With all that said above, there is of course no more over the air. But the traps accuracy, especially the 21.25MHz and 27.25MHz traps are important to obtain the correct Video IF response shape.

So I was able to salvage one core slug out of the 2 in T-103. At this point I don’t have another slug with the coarse thread pitch of the original. I’ve looked on eBay for similar substitutes with no luck. There is a Merit trap coil that is available that’s close. I think this trap is 21.25/22.0 and the Merit trap is 21.25/21.8. I’m wondering if that’s close enough to do some creative tuning to get it to work in the RCA

The trap in the RCA is mutually coupled to the 21.9MHz tuned stage part of the stagger tuned strip and you really must replace it with the same. It will be easier to fix the RCA transformer.

Looked like the other slug is smashed. Did you damage the coil former encased by the bakelite cover?

If the rest is intact and you need only the core. If the only replacements you have have a finer thread but is of the same diameter, that would work as the slug make the thread in the tube.

Can you show some more pictures? What is the diameter of the slug?

Don't know if the coils in a KCS-47 will have the slugs you need, but I did scrap one and kept the coils. If I can find them and one has what you need I'd sell it.

Don't know if the coils in a KCS-47 will have the slugs you need, but I did scrap one and kept the coils. If I can find them and one has what you need I'd sell it.

I believe the slugs in a KCS47 are the same going back to the KCS28. So that should work.

Don't know if the coils in a KCS-47 will have the slugs you need, but I did scrap one and kept the coils. If I can find them and one has what you need I'd sell it.

That would be great Tom. I’ll take whatever you have. PM me. Bob too. My fear is these other slugs have been manipulated way too much and may be fragile as well.

Could you show us a photo of the tool you are using to adjust the slugs?

Could you show us a photo of the tool you are using to adjust the slugs?

Both are plastic tools

https://imagizer.imageshack.com/v2/1024x768q70/924/Jqj9vt.jpg

I found another core to go in to possibly work as a secondary in the trap but it's longer than the original core for T-103. Could that possible work?

Could this possibly work as a substitute? It's 21.25mc primary and 21.8mc secondary trap.

https://imagizer.imageshack.com/v2/1024x768q70/923/v2R516.jpg

What is the Merit no.? Looks like TV-107? If it is specified as an RCA replacement maybe.

I looked up TV-107. It is listed as a convertor transformer with the sound take off similar to the RCA transformer. It was likely used on full split sound sets with sound take off at the convertor. One thing I feel is the trap of the origial spread out on the bakelite frame will have a higher Q. It means that the trap in the RCA provides a deeper null. This may be important when adjust the bandwidth with the 22.1 marker. It means that you may need to modify the alignment procedure to narrow the video IF bandwidth slightly to reduce sufficiently audio carrier passing the remaining video IF stages. Although there is a second 21.25 MHz trap down stream. It is a flip.

It can be made to work but I would prefer the originality.

I agree but if I cannot save these coils, I'm not sure originality can be at the top of the priority list. Silly question next...I do have an RCA 630 spare parts chassis. The traps are of a different form factor but they will fit the chassis mounting holes. They would be able to make the adjustments for this KCS 28 chassis I think. Thoughts from anyone?

The coil you are replacing T103 is a combined video stagger tuned stage and sound take of at the trap. The 630TS chassis is of an earlier generation and it is not compatible.

The coil you are replacing T103 is a combined video stagger tuned stage and sound take of at the trap. The 630TS chassis is of an earlier generation and it is not compatible.

Got it. If you could give me an opinion of an earlier question? I have found another threaded core (ferrite I imagine?) but it's about 1/8th" longer than the core I broke. Do you think that core might work adequately enough to give it a try?

The coil you are replacing T103 is a combined video stagger tuned stage and sound take of at the trap. The 630TS chassis is of an earlier generation and it is not compatible.

So this is sort of a early Intercarrier type set?
Tapping off audio at the 3rd IF it looks like.

So this is sort of a early Intercarrier type set?
Tapping off audio at the 3rd IF it looks like.

RCA did not begin using the intercarrier design until about 1951-52.

No the sound take off is still before the video detector, hence split sound. The idea was to suppress the sound carrier as much as possible prior to the video detector to prevent a 4.5MHz carrier beat. The factor being this set has a wider video bandwidth set compared to most others and the the baseband video response is beyond 4MHz in this set making a 4.5MHz beat more visable.

This chassis hower does take advantage of the first two stages of amplification to provide extra gain.

It's a bit confusing to me what is and what is not! :D

Cause i see early BW sets with it pulled off after the video detector, and also color sets 45.75mh/41.25mh with it tapped from the 3rd IF before the video detector.
:scratch2:

It's a bit confusing to me what is and what is not! :D

Cause i see early BW sets with it pulled off after the video detector, and also color sets 45.75mh/41.25mh with it tapped from the 3rd IF before the video detector.
:scratch2:

Colour sets pull the sound off before the video detector to minimize the 4.5MHz beat. You will also notice colour sets have another detector after the 3rd IF which is in effect an intercarrier mixer to extract the intercarrier sound.

The intercarrier sound process was desirable because the audio is available over a wide range of the fine tuning control. In otherwords with intercarrier sets you can fine tune for best picture and not worry about the sound. Split sound sets the tuning is for best sound. Which means the Video IF alignment for split sound sets is more critical because if the video carrier is not EXACTLY at 45% on the nyquist slope on the IF resesponse when the sound is 21.25MHz for the spit sound IF channel, the picture will either be soft or excessively noisy.

You want these black coils - right?
https://live.staticflickr.com/65535/54017591420_a7a1748cde_c.jpg (https://flic.kr/p/2qimgZ7)

OMG yes! You are The Man!

…and just clip off the connections underneath…easiest and least amount of work

Probably will get back on this when Bob can get the coils to me. My intention is to replace T-103 without changing the position of the slugs and look at the overall IF response to see if my messing with the other traps has caused the alignment to become a mess. If it can be salvaged by installing a T-103 unchanged from its original tuned state then I’ll leave it at that. If I find the other traps are so misaligned retuning them is going to be very difficult I’ll replace them with the other 2 additional traps with their original tuning and see what the overall IF looks like. Bob has so much going on it may be a bit before he can harvest and get the traps to me so this thread might go on hiatus for a while.

Probably will get back on this when Bob can get the coils to me. My intention is to replace T-103 without changing the position of the slugs and look at the overall IF response to see if my messing with the other traps has caused the alignment to become a mess. If it can be salvaged by installing a T-103 unchanged from its original tuned state then I’ll leave it at that. If I find the other traps are so misaligned retuning them is going to be very difficult I’ll replace them with the other 2 additional traps with their original tuning and see what the overall IF looks like. Bob has so much going on it may be a bit before he can harvest and get the traps to me so this thread might go on hiatus for a while.

Don't lose confidence! You just have to apply logic and patience. To apply logic, you need to know how it works and what you are doing.

With regards to T-103, you will not be able to leave it as is as circuit variances will affect tuning.

Let us return to the procedure. Since you impatiently began to adjust things before we logically analysed, it means going thru the procedure once again and stopping after the completion of each stage to discuss and not jumping forward prematurely.

In this way you will have a near perfect alignment on this set and you will have gained the knowledge and experience to apply to future alignments.

Don't lose confidence! You just have to apply logic and patience. To apply logic, you need to know how it works and what you are doing.

With regards to T-103, you will not be able to leave it as is as circuit variances will affect tuning.

Let us return to the procedure. Since you impatiently began to adjust things before we logically analysed, it means going thru the procedure once again and stopping after the completion of each stage to discuss and not jumping forward prematurely.

In this way you will have a near perfect alignment on this set and you will have gained the knowledge and experience to apply to future alignments.

Thanks for that advice. Yes, when I reached the step where the top of T-103 needed to be adjusted by monitoring the voltage on the VTVM, I got very heavy handed (literally, I broke the damn thing!). Part of this was, yet again, another piece of faulty equipment...my VTVM. I wasn't getting anything more than a weak swing of the needle even in the 1.5V range and subsequently, began moving the upper slug all over on T-103. I have since acquired another one that was restored, calibrated and tested. It has much greater sensitivity than the brick I was using.

I think you had mentioned it might be useful to look at the overall response curve to check where tweaks are needed. I guess these adjustments may be so far off now that what you said below isn't an option anymore?


"I should have said on the outset of this adventure, normally the alignment is fairly close. The sound IF is narrower bandwidth and is best gone over more concisely. The traps too need a little adjustment but they should be fairly close.

Because the video IF stagger tuned stages are pretty tuned for a broad response, there was really no need to perform the steps to spot align each stage. All that needed to be done was first sweep the overall video IF and only perform a few touch ups to get the response in the manual. I would only resort to deeper investigation if the response is bad and not easily corrected."

Are these the right part #s?
https://live.staticflickr.com/65535/54026711020_3ee0c33e45_z.jpg (https://flic.kr/p/2qja1VA)

Are these the right part #s?
https://live.staticflickr.com/65535/54026711020_3ee0c33e45_z.jpg (https://flic.kr/p/2qja1VA)

Yes sir. You got my address and message regarding your time?

The part no.s do not match the 8T241.

What model were they from?

I don't recall. I think I just got it as a bare chassis. Sure looks the same as an 8T241 chassis

They are the same traps in my KCS 28B chassis for the 9TC-240

This has always been about the alignment of the 9TC-240 (see title). The part numbers match the traps in my set exactly

They look the same. And the one at the far right looks like T-103.

Also the earlier photo of the chassis looks like the layout of the KCS-28.

I think they will work. At least we will make them work.

They look the same. And the one at the far right looks like T-103.

Also the earlier photo of the chassis looks like the layout of the KCS-28.

I think they will work. At least we will make them work.

Yes we will...slowly and gently...aligning together...forever! :yes::yes::yes:

Sounds like a twilight zone episode.
https://live.staticflickr.com/65535/54025655247_9ee1da7e57_z.jpg (https://flic.kr/p/2qj4B5B)

Feels more like “The Outer Limits”

Not jumping ahead...can't anyway but, at Penthode's suggestion, I made these to facilitate step 16 and shunting the primary windings of the primary coils of the indicated transformers. The resistor is 330 ohms. Should make things a bit cleaner than tacking them in when the time comes.

https://imagizer.imageshack.com/v2/1024x768q70/923/6rru0F.jpg

https://imagizer.imageshack.com/v2/1024x768q70/923/RcT4E4.jpg

Your 330 ohm shunts look similar to mine except yours look more snazzy.

Stuff like that when done goes into my alignment box where in the past i have created cable extenders and jigs to assist alignments. There is a good chance yoy will need them again someday.

Well I’m just trying to be productive until Bob gets the parts to me. Once I get through this experience I have a Crosley that’s essentially a Dumont clone and the sound and video if circuits are all kinds of messed up. That would be next on my to do list. How different is the alignment protocol on different early RCA sets? I have a 630 in the works but on the shelf for now

Well I’m just trying to be productive until Bob gets the parts to me. Once I get through this experience I have a Crosley that’s essentially a Dumont clone and the sound and video if circuits are all kinds of messed up. That would be next on my to do list. How different is the alignment protocol on different early RCA sets? I have a 630 in the works but on the shelf for now

The alignment is similar. I suspect the Dumont is easier. I know the RCA 630TS is simpler.

Coils were shipped out earlier today. Should be there in a couple days.

Thank u so much!

Replacement trap coils should arrive today. I'll be getting back on the alignment procedure late tonight or early tomorrow. My intention is to replace the T-103 transformer I broke and start the coil adjustment with the VTVM over. Hopefully, Penthode will see the post and guide me once again!!!

Coils are here. Thank you Mr Andersen.

Replacement T-103 is in. I think the best strategy is to go back to step 6 in the alignment. I didn't do anything to change the discriminator or sound IF response curves in steps 1-4.

I rechecked the discriminator and sound IF response curves anyway and they are perfectly symmetrical are the markers are correct. I think I should wait for some experiential brain input. I don't know if we should go through all of the transformer primary and secondary coil adjustments one at a time or skip to the overall look at the T-1 and T-101 trace in figure 15 and the overall IF RF response trace in figure 16 and see how much off these marker frequencies are from the service data. Maybe minimal adjustments are needed

I think first checking and confirming the traps are correct. Following the RCA notes is best. But do it slowly and step by step.

Remember that it is easy to tune incorrectly and make the IF strip break into oscillation. We it is oscillating, it will give false reading. As pointed out, you and test if it is oscillating if you get a large signal at the video detector when the signal generator is off.

If it does break into oscillation, the notes suggest the solution.

The main thing is if the slugs appear tight, don't force them. Stop and let's discuss

I think first checking and confirming the traps are correct. Following the RCA notes is best. But do it slowly and step by step.

Remember that it is easy to tune incorrectly and make the IF strip break into oscillation. We it is oscillating, it will give false reading. As pointed out, you and test if it is oscillating if you get a large signal at the video detector when the signal generator is off.

If it does break into oscillation, the notes suggest the solution.

The main thing is if the slugs appear tight, don't force them. Stop and let's discuss

Yes top of T-103 is not turning. Using a plastic tool with the tip formed to fit exactly the slot on top of the slug.

Yes I anticipated you might run into this. I would be inclined to remove the slug and use it on the original transformer. That is if you did not damage the original transformer when trying to remove the broken slug.

To loosen and remove the slug, you might try first a drop of mineral spririts to dissolve the wax.

A further solution which I have done on these sets is to remove the transformer and disassemble it. I use a heat gun gently on the tube holding the slug and heat it until the slug moves. I remove the slug, checheck the tube and ensure the slug moves with sufficient friction to hold it in place but loose enough to adjust.

Try the mineral spirits (turpentine) first. Add a drop and leave it a few minutes and then try to adjust.

The other slugs on the other transformers I assume are near where they originally were and can move enough for the touch up adjustment?

Remember, there is nothing magic about these transformers. I have replaced and made many coils and transformers for various sets. I have successfully remade the quadrature coil used in early Zenith color sets which are prone to going brittle and snapping. I have even reused the original wire failing to have on hand the correct gauge wire. It is just logic and perseverence.

I will try the mineral spirits first very conservatively. I have disassembled several coils like these in the past and I’ve been surprised at how much space is in these Bakelite shells. The coil windings are around a cylinder that’s thinner than a pencil. The damn problem is finding the sweet spot between downward pressure on the tool enough to keep it seated in the slot without so much the core is pushed out of the threads and down. This is really the only adjustment that’s significantly displaced from where they were originally. I have pictures of the chassis bottom and the screw type if coil threads are the same as they were before I started messing this up. Let me see what a little lube will do. I don’t want to put a drop of spirits in the core. I think I’ll soak a Q Tip in it and place the cotton end in the tube and just press a small amount out

I do't believe you need to provide much downward pressure if the screwdriver tip properly seats in the slot. With a good slug removed, you may wish to check the fit and alter the tool as necessary to provide a good fit.

Will do. The top slug in T-103 is stuck solid. Ill use the mineral spirits. I have a variety of petroleum based penetrant lubricants, WD-40, PB Blaster etc but these slugs are compressed iron powder held together with a binder correct? I don't want to do anything that'll compromise that.

It worked! Slug is loose and turns easily. I was able to turn the slug 1/4 turn in either direction from the original position where it sits right now. More to come I'll make the first adjustment shortly if it is needed.

Is the old transformer salvageable? And the transformer you loosened the core is the correct one with the sound takeoff from the tap in the outer trap? T103's dual purpose is the sound take off from the 21.25MHz trap. You will see two wires soldered to the trap: one at the end which connects to the chassis and the other mid point tap which feeds the first sound IF amplifier control grid.

Is the old transformer salvageable? And the transformer you loosened the core is the correct one with the sound takeoff from the tap in the outer trap? T103's dual purpose is the sound take off from the 21.25MHz trap. You will see two wires soldered to the trap: one at the end which connects to the chassis and the other mid point tap which feeds the first sound IF amplifier control grid.

No I don't think the old T-103 is salvageable at this point but I'll keep it. The slugs are broken at the top where the tool tip goes to adjust it. Yes I can probably find substitute cores but for right now, I'm putting it aside.

I actually treated all three traps and their cores with the mineral spirits because I want to avoid any issues with them being stuck if they need adjustment.

Yes, the one being focused on is the T-103 trap and on install of the one Bob harvested from his chassis and sent to me, I soldered the tabs you described so we're good there.

I'll need to get back to you on this. I think I'm doing something wrong in the way I have step 6, the adjustment of T-103 configured. I'm not getting a DC read on the VTVM that's in the suggested voltage range. I'll be more specific on what's going on in a day or so.

I'll be back on this later tonight!!! As I said, I need to be on a much higher scale than the 5 volt scale for the T-103 top coil adjustment with the VTVM ground and voltage leads connected across R119. Something isn't right.

Could the fact my DC probe has an integral 1MOhm resistor in it be causing issues with this nulling measurement? I should be able to center this VTVM no matter what scale I have it on since there's 120V DC on both sides of the resistor correct? BTW, R119 was out of 5% spec at a hair under 6K. I replaced it with a 1% modern resistor at 5.6K

I think I just cooked this VTVM. Stopped working at all and I opened it, disconnected the meter from the board and tested it for continuity. Nothing. I think I fried it. Is there anything I can't eff up?

It is not clear what you are trying to do. Can you explain what step in the procedure you are attempting?

Step 6. 21.25 mhz signal into pin 1 of V-2 through a 1500pf cap. The potentiometer is in place and adjusted so there’s -4.5V at the intersection of R135 and R136. VTVM connected across R119 and wanting to adjust top of T-103 for minimum on the VTVM

One thing I want to understand. With the DC probe and ground from the VTVM attached to either side of R119, what is it I’m seeing on the meter? I actually read the voltage just for grins on the leads on either side and they are about 7 volts of negative DC apart. One side is -120V DC and the other is -127V DC which I guess is the result of passing through the resistor? But regardless what is it I’m measuring and “minimizing” when the trap is being adjusted?

What you are measuring is residual 21.25 MHz which managed to get thru to the video detector load resistor. R119 is the load resistor where the demodulated video signal appears. It is this signal voltage which is amplified by the video amplifier and then fed to the kinescope for display.

As I mentioned before, the detector load resistor signal ground is at -120 volts DC. The reason is the video amplifier is DC coupled to bring the DC component to the picture tube. This means a DC restorer tube is not required. You must understand this. If you do not ask further questions.

When you are adjusting the traps, because the signal is being sucked out by the trap, it is should normally be at a very low level when measured at the video detector. That is likely why you cannot see it. The alignment instructions are a only guide and you must understand what this all means. Because it is a trap and you do not see anything on the VTVM, did you try raising the signal level until you saw the needle deflect? Alternatively, if you reduce the -4.5volt bias to provide more gain, that would raise the signal enough so that you would clearly see the null as you adjust.

Let us know if you do not understand.

Another way to check for signal is to swing the generator either side of 21.25 MHz slightly. As you move each way away from 21.25 MHz, you should find the voltage level rise. That is a good way to check the trap is adjusted properly.

OK. I'm still trying to understand this. You said what I'm measuring on the VTVM is residual 21.25 MHz signal voltage??? Then there's -120V DC in addition that goes to CRT? I guess I need to know more about how this circuit works and what it does. I'm in uncharted waters. At R119 (or around R119 as I'm looking at the schematic) there's a -120 volt demodulated video signal that goes into the video amp. Along with it, there's residual 21.25 MHz voltage that needs to be "tuned out" by adjustment of T-103? The residual voltage would cause an issue with the demodulated signal going into the amplifier tube??? Or am I WAY off base?

I see the measurement point is between the first and second video DC coupled amplifier. What is the question regarding the measurement? It looks to be very straightforward.

OK. I'm still trying to understand this. You said what I'm measuring on the VTVM is residual 21.25 MHz signal voltage??? Then there's -120V DC in addition that goes to CRT? I guess I need to know more about how this circuit works and what it does. I'm in uncharted :thumbsdn:waters. At R119 (or around R119 as I'm looking at the schematic) there's a -120 volt demodulated video signal that goes into the video amp. Along with it, there's residual 21.25 MHz voltage that needs to be "tuned out" by adjustment of T-103? The residual voltage would cause an issue with the demodulated signal going into the amplifier tube??? Or am I WAY off base?
Look at it this way. This set is designed to include a two stage DC coupled video amplifier. Let's go back to basics: why is there a two stage DC coupled amplifier? Next to provide the two stage DC amplifier, the two stages have to be DC stacked. With regards to the cathode and control grid, the plate is roughly at +120vdc. So to DC couple the two stages, the first stage grid/cathode is at about -120vdc, the plate of the first stage is DC coupled to the second stage grid/ cathose at around 0vdc and the plate of the second stage is coupled to the grid of the picture tube at around +120vdc. This is to couple the DC component. Do you understand this?

The video signal at the video detector is only about 1v p-p across R119. But the R119 return is connected to the -120vdc supply to facilitate the DC coupled amplifier.

The DC coupled amplifier is to maintain a consistent black level. Do you understand about black level clamping?

The last thing about the 21.25 MHz sound signal. Why do to think it is to be nulled out of the video channel?

Look at it this way. This set is designed to include a two stage DC coupled video amplifier. Let's go back to basics: why is there a two stage DC coupled amplifier? Next to provide the two stage DC amplifier, the two stages have to be DC stacked. With regards to the cathode and control grid, the plate is roughly at +120vdc. So to DC couple the two stages, the first stage grid/cathode is at about -120vdc, the plate of the first stage is DC coupled to the second stage grid/ cathose at around 0vdc and the plate of the second stage is coupled to the grid of the picture tube at around +120vdc. This is to couple the DC component. Do you understand this?

Can we take this description a concept at a time. The 12AU7 contains the 2 stages of video amplification. This 2 stage, DC coupled amplification happens here? I don't know what coupled refers to here...the 2 stacked DC voltages?

The last thing about the 21.25 MHz sound signal. Why do to think it is to be nulled out of the video channel?

It would leak into the video signal and create unwanted interference?

The video signal at the video detector is only about 1v p-p across R119. But the R119 return is connected to the -120vdc supply to facilitate the DC coupled amplifier.

The DC coupled amplifier is to maintain a consistent black level. Do you understand about black level clamping?

No sir I do not. I just know the basics of the production of a scanned black and white video image based on varying intensity of phosphor luminescence from the intensity and position of the electron beam at any one time on the CRT screen. Is that correct? This scanning from top to bottom horizontally goes back to the top of the screen and creates a new set of beam intensity driven fluorescent intensities on the phosphor...do enough of these scans over a second and you get the illusion of motion. Is that correct?

And just a practical question for the setup in this step...I have the ground lead from the VTVM connected to one side of R119. The DC voltage probe from the VTVM is connected to the other side of the resistor R119. I have a 21.25 MHz signal going into pin one of the 6AG5 converter through a 1500pf ceramic cap. The VTVM is on the 5 volt scale. What do you think the RF signal level should be? They don't specify anything in the instructions.

And when I have this setup and turn the TV on (with the potentiometer installed and adjusted to the -4.5V AGC voltage) the needle deflects on the VTVM off scale. Doesn't matter if I'm reading DC+ or DC-. I cannot use the zero adjust to get it on scale so I can see any sort of "minimizing". The needle is blasted to one side or the other. The VTVM works...I can read the -120 volts in the circuit if I just do a basic measurement but in the either side of the resistor setup, I can't get the needle on scale. It just fully deflects to one side or the other depending on if it's set to read + or - DC volts.

If I were to connect my DVM across R119 that is supposed to have -120V DC on both sides, what should I see on the meter? I think I'm confused as to what the meter is measuring in this configuration. If I connect the ground lead to chassis ground, I would see -120V DC if I put the voltage probe on either side but what exactly am I looking at on the meter when It's connected as part of the DC line?

No sir I do not. I just know the basics of the production of a scanned black and white video image based on varying intensity of phosphor luminescence from the intensity and position of the electron beam at any one time on the CRT screen. Is that correct? This scanning from top to bottom horizontally goes back to the top of the screen and creates a new set of beam intensity driven fluorescent intensities on the phosphor...do enough of these scans over a second and you get the illusion of motion. Is that correct?
The setting of a reference black in a display is a long discussion that is as old as television itself. It is the need to define a black in the display and maintain the black with changes in video content. DC coupling provides this and is the reason that the designers of this set we t to the trouble of providing DC coupling between stages. Notice there are no coupling capacitors between the stages which would block the passing of DC changes .

The video amplifier of this set maintains the black level very well by passing the DC component which sets the black reference. Another method employed by the RCA 630TS which preceded this set was the use of a DC Restorer. Note all modern displays employ black level clamping. Interestingly, thru the1950s and 1960s, sets dispensed with the DC clamping. This meant that the black level drifted upward in dark scenes and blacks were darker in a bright scene.

The topic of DC restoration or lack of in later sets is seen as a problem by many. Just be aware that the strange design of the set with the -120v DC supply and the stacked stages was to provide the proper consistent black reference that later sets did not have.

It is a topic well discussed in this forum.
https://www.videokarma.org/showthread.php?t=248278

The setting of a reference black in a display is a long discussion that is as old as television itself. It is the need to define a black in the display and maintain the black with changes in video content. DC coupling provides this and is the reason that the designers of this set we t to the trouble of providing DC coupling between stages. Notice there are no coupling capacitors between the stages which would block the passing of DC changes .

The video amplifier of this set maintains the black level very well by passing the DC component which sets the black reference. Another method employed by the RCA 630TS which preceded this set was the use of a DC Restorer. Note all modern displays employ black level clamping. Interestingly, thru the1950s and 1960s, sets dispensed with the DC clamping. This meant that the black level drifted upward in dark scenes and blacks were darker in a bright scene.

The topic of DC restoration or lack of in later sets is seen as a problem by many. Just be aware that the strange design of the set with the -120v DC supply and the stacked stages was to provide the proper consistent black reference that later sets did not have.

It is a topic well discussed in this forum.
https://www.videokarma.org/showthread.php?t=248278

I will check it out...Thank you P

OK...I got the top adjustments done for the traps and transformers. The issue was with the signal strength. The ideal was around 75mV. I was able to minimize the meter output on the VTVM at the 5V level and was able to switch to the 1.5V scale to make very fine adjustments down to an absolute minimum. I'm going to start the maximum adjustments on the bottom cores tomorrow. I may need to apply some mineral spirits to the trap bottom cores to be certain they are loose. All of the VTVM off scale issues had to do with the signal strength being much higher than needed. I found the signal strength sweet spot and the core adjustments were easy...like they're supposed to be

Looks like you are getting the knack.

Well my friend and part time mentor, you and the others who said this TV would be the hardest thing I’ll ever do in this hobby were absolutely right! I’m nowhere near finished with it yet but I think (I hope) I may be getting close to the other side of feeling lost. I believe I can probably deal with the next series of transformer and trap adjustments on the bottom cores but please, nobody abandon this ship just yet!!!!!! The next step after that will be looking at the overall response curve using the 330 ohm shunts I made and there are some steps in that protocol I’ll need help with. Thank you again for your help!

All bottom cores have been adjusted passing a signal indicated in the service notes. I want to move on to the next step of the picture IF transformer adjustments. This involves shunting the primary coils of T-102, 103, 104 and 106 with a 330 ohm resistor. I have the resistors soldered to mini alligator clips and can do this easily. That is, If I can figure out what bottom terminals are for the primary coil in each. Here is the schematic section with the transformers and the letters of the tabs shown.

https://imagizer.imageshack.com/v2/1024x768q70/923/JuswcG.jpg

https://imagizer.imageshack.com/v2/1024x768q70/923/WWkQN4.jpg

Are the secondary coils the ones that are standing alone without being connected to the circuit, except for T-103 where the secondary (I think) is where the sound takeoff goes to the 6AU6 grid in the sound IF circuit?

Here is what I have setup:
1. Tuner tuned between channels 13 and 2.
2. Potentiometer adjusted so the voltage at R135/136 is -2.0V DC
3. Sweep generator at a 25MHz center frequency with a symmetrical sweep from 20
to 30 MHz.
4. Sweep output at 300mV
5. Generator RF out connected to pin 1 grid of the converter (V2) through a 1500pf
capacitor.
6. Oscilloscope connected to Pin 1 of the 12AU7 Video amp (V106).
7. Transformers shunted with a 330 ohm resistor in the following way
T-102 Tabs A and B
T-103 Tabs A and D
T-104 Tabs A and B
T-106 Tabs C and D
8. HP 8600A Digital Marker Generator set for 25MHz center frequency marker and
22.05 and 24.75 MHz additional markers.

With this setup and the scope in XY mode, I get a trace that isn't flat but the amplitude is very low where it does deviate and changing the signal strength through the available voltages doesn't affect it much. I do not want to touch the T-1 and T-101 transformers used to adjust this until I get some feedback I have all of this correct.

"With this setup and the scope in XY mode, I get a trace that isn't flat but the amplitude is very low where it does deviate and changing the signal strength through the available voltages doesn't affect it much. I do not want to touch the T-1 and T-101 transformers used to adjust this until I get some feedback I have all of this correct."

The voltage you set with the potentiometer is the IF gain control. The resulting gain will depend on the exact gain control characteristics of the particular tubes you have. You can try adjusting the potientiometer slightly to get the output signal strength you expect/need.

I concur. The shunting of the coils with the 330 ohm resistors will mean the gain is reduced. You may try reducing the bias a tad with the rheostat. Also you may need to raise the signal a bit.

You want to ensure the curve does not appreciably change with signal level and bias change. That you can verify raising a lowering the signal a bit.

Ok thanks for the input. Can someone please check me I have the shunting resistors correctly connected? It says to shunt the primary coil of each of the four. Am I correct that the primary coils are the ones in circuit and the secondary coils are stand alone?

There are no secondaries. What you are calling the secondaries are the traps. The stages are capacitively coupled not transformer coupled except for the link between the mixer and 1st Video IF stage.

You are shunting each of the coils.

Do you understand why you are shunting the coils with the resistors?

There are no secondaries. What you are calling the secondaries are the traps. The stages are capacitively coupled not transformer coupled except for the link between the mixer and 1st Video IF stage.

You are shunting each of the coils.

Do you understand why you are shunting the coils with the resistors?

No you have lost me. I guess transformer is the wrong term. I don't know what "capacitively coupled" means. I think the purpose of the traps was discussed before and at one point I had the concept but now I'm not sure. I think I remember they were to "trap" and eliminate certain frequencies from the video signal minimizing interference but the only one I recall being discussed was T-103 and the 21.25MHz trap.
There are a lot of terms I listen to without completely understanding them. I know the standard definition in everyday life of the word "coupled" but in electronics I'm not so sure. Most of what has been talked about leads me to think when 2 things are "coupled", one affects the other despite not being directly connected. Is this correct? Capacitively coupled??? Nope. Loosely coupled??? Nope

There are no secondaries. What you are calling the secondaries are the traps. The stages are capacitively coupled not transformer coupled except for the link between the mixer and 1st Video IF stage.

You are shunting each of the coils.

Do you understand why you are shunting the coils with the resistors?

When the instructions say "shunt the primaries" I just assumed there were secondaries

When the instructions say "shunt the primaries" I just assumed there were secondaries

Funny. I went back and looked at the instructions and it calls the units transformers and calls the coils "prim." implying primary. Semantics.

The main issue is the coils are stagger tuned to cumulatively provide the wide bandwidth required. The shunting of the coils with the 330 ohm resistors is to effectively remove each tuned IF stage so that the response will be governed only by the tuner to 1st IF over coupled transformer link.

"Coupled" simply means "connected." The means of connection can be a transformer or a capacitor, or less commonly, a resistor or inductor.

Funny. I went back and looked at the instructions and it calls the units transformers and calls the coils "prim." implying primary. Semantics.

The main issue is the coils are stagger tuned to cumulatively provide the wide bandwidth required. The shunting of the coils with the 330 ohm resistors is to effectively remove each tuned IF stage so that the response will be governed only by the tuner to 1st IF over coupled transformer link.

In the schematic, what do the twin up and twin down arrow designations next to the coils mean?

In the schematic, what do the twin up and twin down arrow designations next to the coils mean?

I assume that's to denote an adjustable core type coil on the schematic.

Could the arrow directions indicate the top core and bottom core? Not sure.

Or, perhaps it means coils that can be adjusted from both the top or bottom of the chassis? I am seeing the same thing on color set schematics, that i know have one core, but when i look at the convergence board that can only be done from above, it has a one way arrow

I thought adjustable had a diagonal through it. I’ve looked in a dozen schematic symbol lists and I can’t find a thing

There is no real standardization. But in RCA lingo from other equipment, the parallel lines means a ferrite core and the arrows point to where it is to be adjusted.

So what tabs on these things am I shunting with the resistors? I haven’t gotten a clear answer for that. I listed the setup and posted the schematic previously but I didn’t get any information. Is it the up arrow side of the coils being called the primaries?

So what tabs on these things am I shunting with the resistors? I haven’t gotten a clear answer for that. I listed the setup and posted the schematic previously but I didn’t get any information. Is it the up arrow side of the coils being called the primaries?

The arrows pointing up mean the trap adjustment is on the top of the chassis. The arrows pointing downmeans the adjustment for the stagger tuned stage is made from under the chassis. Each stagger tuned stage has a resonant coil which connects to T102 terminals A/B and T103 terminals A/D, T104 terminals A/Band and T106 terminals D/C.

The resistors are placed across each stagger tuned coil. There is really no primary and I don't know why you are hung up on that. There is the stagger tuned coil and the parallel tuned trap mutually coupled to it. It is clearly identified on the schematic.

Do you understand what you are doing by clipping in place the resistors? It is to eliminate the resonance of the stagger tuned coils so that the remainder of the video IF strip is just an untuned amplifier. This is so you can see independently the tuner over coupled transformer link frequency response when you sweep it. You must try and understand the process so so will be better able to identify and rectify any problems.

I guess this reference in the instructions is why I keep referring to them the way I do:

https://imagizer.imageshack.com/v2/1024x768q70/924/2k64Rs.jpg

The arrows pointing up mean the trap adjustment is on the top of the chassis. The arrows pointing downmeans the adjustment for the stagger tuned stage is made from under the chassis. Each stagger tuned stage has a resonant coil which connects to T102 terminals A/B and T103 terminals A/D, T104 terminals A/Band and T106 terminals D/C.

The resistors are placed across each stagger tuned coil. There is really no primary and I don't know why you are hung up on that. There is the stagger tuned coil and the parallel tuned trap mutually coupled to it. It is clearly identified on the schematic.

Do you understand what you are doing by clipping in place the resistors? It is to eliminate the resonance of the stagger tuned coils so that the remainder of the video IF strip is just an untuned amplifier. This is so you can see independently the tuner over coupled transformer link frequency response when you sweep it. You must try and understand the process so so will be better able to identify and rectify any problems.

https://imagizer.imageshack.com/v2/1280x1024q70/923/C3Ofqq.jpg

Each stagger tuned stage has a resonant coil which connects to T102 terminals A/B and T103 terminals A/D, T104 terminals A/Band and T106 terminals D/C.

So the "resonant coil" in this example (T-106) is the coil that's in circuit?

The resistors are placed across each stagger tuned coil. There is really no primary and I don't know why you are hung up on that.

I'm confused. Can you clarify for me the difference between the resonant coil and the stagger tuned coil? You refer to the "stagger tuned stage". I guess that's confusing to me as well.

Basically I think I need to know what is in these cans. For the pictured T-106, the can is literally the stagger tuned stage? The 2 coils within it...the coil between D and C is the resonant coil. Is this correct? What is the other coil, the one that stands alone and is not connected in the circuit? Or am I looking at this the wrong way and I need to think of the 2 coils in the stage as a single item? :scratch2::scratch2::scratch2::scratch2:

Yes, d&c are the resonant. The other (without connections to the circuitry) is the trap.

Each coil connected through capacitors or otherwise to the tube circuits is a resonant coil. Saying that they are stagger-tuned coils only means that each one is tuned to a different frequency instead of all to the the same frequency (which is called synchronous tuning).

The coils that are connected to nothing except a single capacitor and nothing else are the trap circuits. These trap circuits can be called magnetically coupled or transformer coupled if you wish.

Yep, yep and yep to the previous replies.
All that stagger tuning is is to have each tune circuit tuning staggered to obtain the desired wide bandwidth. Later, when you get to the point where you are frequency sweeping the entire IF amplifier, you will have to slightly tweak some of the stages to get the flat top shaped response with the frequency markers at the correct amplitude. And because the stages are stagger tuned, you will look at the response on the scope and adjust one of the stagger tuned stages corresponding to the part of the band to correct it.

So my brain needs to flush all this out to be able to understand it. It’s just the way facts have to get processed before I get it. So when a signal with different frequencies goes through a circuit and you are trapping one or removing one with a trap coil, that coil, by moving an iron slug to the appropriate position within a winding will resonate at the desired frequency matching the signal to be filtered out. Is it the coil in circuit that is resonating at various frequencies including the one to be trapped and that energy is dissipated by the fact there’s an adjacent coil at just the right “stimulateable” resonance that essentially sucks the frequency energy out of the broader signal? It’s like a filter that hijacks the undesirable frequency out because it’s tuned to “pick it up” from the broadband family of frequencies passing through? Or am I lost somewhere in the asteroid belt!

You got it. The trap circuit sucks a narrow range of frequencies out of the broader circuit's response.

You got it. The trap circuit sucks a narrow range of frequencies out of the broader circuit's response.

And it's the "passive" coil that does this? It does that because the slug and coil are positioned so its natural resonance is at the undesired frequency. When the powered broadband signal goes through the connected coil, the energy associated with the unwanted frequency starts vibrating the tuned passive coil. The energy needed to do this formally resided in the broadband signal at the trap frequency. It is transferred to the trap coil vibrating it and eventually dissipated as heat (Not that it's important...just trying to follow the energy)????????

And it's the "passive" coil that does this? It does that because the slug and coil are positioned so its natural resonance is at the undesired frequency. When the powered broadband signal goes through the connected coil, the energy associated with the unwanted frequency starts vibrating the tuned passive coil. The energy needed to do this formally resided in the broadband signal at the trap frequency. It is transferred to the trap coil vibrating it and eventually dissipated as heat (Not that it's important...just trying to follow the energy)????????

Yes

The wonderful world of the RLC circuits!

Do you understand what you are doing by clipping in place the resistors? It is to eliminate the resonance of the stagger tuned coils so that the remainder of the video IF strip is just an untuned amplifier. This is so you can see independently the tuner over coupled transformer link frequency response when you sweep it. You must try and understand the process so so will be better able to identify and rectify any problems.

So what is it I'm stopping by attaching the resistors? Is it the resonant, in circuit coils or the trap coils? I sorta get the statement this makes the video IF stages an untuned amplifier but the statement "This is so you can see independently the tuner over coupled transformer link frequency response when you sweep it"is making my head spin. So when I sweep the input signal symmetrically 10mc with 25mc as the center frequency (from 20-30mc) and pick it up on the scope at the end of its travel through a detuned IF series of stages, I'll see the full bandwidth signal out at the end? If so why is that important to see and what then am I looking for to adjust?

So what is it I'm stopping by attaching the resistors? Is it the resonant, in circuit coils or the trap coils? I sorta get the statement this makes the video IF stages an untuned amplifier but the statement "This is so you can see independently the tuner over coupled transformer link frequency response when you sweep it"is making my head spin. So when I sweep the input signal symmetrically 10mc with 25mc as the center frequency (from 20-30mc) and pick it up on the scope at the end of its travel through a detuned IF series of stages, I'll see the full bandwidth signal out at the end? If so why is that important to see and what then am I looking for to adjust?

The resistors temporarily shunting the coils will essentially make the IF amplifier downstream a broadband untuned amplifier. This will allow you to see only the tuner to first IF over-coupled link frequency response without interference. You want to be able to establish a correct response between tuner and first IF before adjusting the remaining stages. So the order of work is:

1. Confirm traps are correct
2. Sweep align the tuner to first IF over-coupled link with resistors shunting the downstream stages
3. Sweep align the entire video IF with the resistor shunts removed.

You should be cognizant of the fact that unless someone has in the past meddled with the tuner-1st IF link transformers, the adjustment should be close. Be aware that if any of the resistors are not connected or loose, it will distort the response you are trying to obtain.

Once the resistors are removed which will raise the gain of the IF amplifier, there is the danger of oscillation which they describe how to handle in the notes. The oscillation will occur if two of the stages are tuned close to the same frequency. The Video IF stages must be properly stagger tuned to be stable.

Here is a Wiki page describing stagger tuning.

https://en.wikipedia.org/wiki/Staggered_tuning#:~:text=Staggered%20tuning%20is%2 0a%20technique,the%20expense%20of%20reduced%20gain .

The resistors temporarily shunting the coils will essentially make the IF amplifier downstream a broadband untuned amplifier. This will allow you to see only the tuner to first IF over-coupled link frequency response without interference. You want to be able to establish a correct response between tuner and first IF before adjusting the remaining stages. So the order of work is:

1. Confirm traps are correct
2. Sweep align the tuner to first IF over-coupled link with resistors shunting the downstream stages
3. Sweep align the entire video IF with the resistor shunts removed.

You should be cognizant of the fact that unless someone has in the past meddled with the tuner-1st IF link transformers, the adjustment should be close. Be aware that if any of the resistors are not connected or loose, it will distort the response you are trying to obtain.

Once the resistors are removed which will raise the gain of the IF amplifier, there is the danger of oscillation which they describe how to handle in the notes. The oscillation will occur if two of the stages are tuned close to the same frequency. The Video IF stages must be properly stagger tuned to be stable.

Here is a Wiki page describing stagger tuning.

https://en.wikipedia.org/wiki/Staggered_tuning#:~:text=Staggered%20tuning%20is%2 0a%20technique,the%20expense%20of%20reduced%20gain .

Thank you. I have not messed with T-1 and T-101 so hopefully they are close. Still not clear on where to clamp the resistors...for example, on T-102, I am putting the resistor between tabs A and B correct? I'm not shunting the trap coil correct?

A caution I need to add with this particular chassis when adjusting the IF stages. The adjustments can be deceptive because when you are adjusting for a peak you may inadvertently be tuning two stages to the he same frequency which will cause oscillation. This oscillation can be easily mis identified as a peak. The way to confirm is always as you raised or lowered the deep generator input, the output put level should rise and fail. If when reducing the signal generator in you still see a signal which does not change when you vary the generator output, you have an oscillation condition you will need to address.

Yes as you have said. Not gonna tell me which coil gets the shunt eh?? That’s ok…I’ll figure it out!:scratch2::scratch2::scratch2:

Yes as you have said. Not gonna tell me which coil gets the shunt eh?? That’s ok…I’ll figure it out!:scratch2::scratch2::scratch2:

I told you! Even down to the connection letters written on the base of the transformers!

The arrows pointing up mean the trap adjustment is on the top of the chassis. The arrows pointing down means the adjustment for the stagger tuned stage is made from under the chassis.
Each stagger tuned stage has a resonant coil which connects to T102 terminals A/B and T103 terminals A/D, T104 terminals A/B and T106 terminals D/C.

The resistors are placed across each stagger tuned coil.
There is really no primary and I don't know why you are hung up on that. There is the stagger tuned coil and the parallel tuned trap mutually coupled to it. It is clearly identified on the schematic.

Do you understand what you are doing by clipping in place the resistors? It is to eliminate the resonance of the stagger tuned coils so that the remainder of the video IF strip is just an untuned amplifier. This is so you can see independently the tuner over coupled transformer link frequency response when you sweep it. You must try and understand the process so so will be better able to identify and rectify any problems.

Here is is again

Just making a joke…not a very good one I guess. Sorry if I offended you.

I am never offended. That was my joke in return. I hope it did not offend you.

Are you all set? A good part of the process is identifying the pitfalls and knowing how to get out of them. I try to (and not always successfully) abide by the rule if something doesn't look right, stop and think about it before proceeding.

So I went back to step 6 in the alignment procedure just to be certain the adjustments I made to the top and bottom cores with the different frequencies fed into the converter grid were accurate and that the VTVM was reading the minimizing/maximizing accurately i.e. checking my work that I had the trap coils tuned to the correct resonant frequencies and the IF stages tuned properly. A couple of days ago, I posted the issue with the VTVM going off scale was tied to the signal strength going into the converter and with careful adjustment of the signal output I was able to tune the traps and stages accurately without the VTVM requiring a voltage range setting higher than 5 volts DC. When rechecking tonight, I encountered the same issue. I could not get the VTVM to read in the 5V scale when measuring across the video amp load resistor.

I believe I've found what is doing this but how and what is happening I don't know. The brightness control seems to be a problem. It is intermittently grounding out and sending full voltage through the yellow wire to the CRT. A bright horizontal line appears on the screen. Touching the shaft will cause the VTVM to jump way out of range. I don't know if this is what is causing the issue with measuring the voltage changes that happen when I'm trying to tune traps and minimizing at the R119 load resistor but when it happens, the VTVM pegs and goes off scale.

I don't see how sending full voltage to the CRT cathode could be causing the issue. The only possible link I see may be the fact the yellow wire from the control to the CRT cathode runs directly under the load resistor I'm measuring to adjust the frequencies in the various stages. This has been an intermittent issue since I started doing this series of adjustments and I guess, when I worked on it a few days ago and reported no problems, it wasn't happening. So at this point, I don't know if I even have the trap coils adjusted correctly. I don't know enough about what that voltage spike in proximity to a test point in this effort could do. I guess I could move the wire and see if it helps.