I would like to share my current project, a Packard Bell 1968 color TV, model CQ-956. The TV was purchased and remained here locally with it currently belonging to the original owner's grandson. Searching old ads would suggest this TV cost $599 ($4,500 in today's money).

Most of my project are old radios but this TV was too nice to not bring home, I have fended off several comments to convert it into a fish tank. My goal is to get it working to play old games, catching local TV news, and maybe some movies, probably 1 - 4 hours runtime per week.

https://i.imgur.com/BxLE9TQ.jpg

https://i.imgur.com/dqw87no.jpg

I have so far replaced all of the electrolytic capacitors and swapped out the tubes with a set of NOS and/or tested good tubes (maybe unnecessarily). For now I am feeding signal in on channel 3 or 4 via a NES game console. Once powered on I get sound and picture, this is a very good start as there could have been countless issues to fix just to get to this point.

Now the picture is dim, fuzzy, and only displays black and white. High voltage measures about 26K which is a bit high and the big issue is after 5 minutes the high voltage cage starts to make a hissing noise, the horizontal tube starts to glow red, and then the internal breaker trips out. I do have a thread open on the Antique Radios forum and was suggested to look at some of the coupling capacitors feeding the horizontal output circuit. I am currently working on this along with sourcing two amperage meters to monitor and set the horizontal sweep circuits. My fear is that the issue is a failing flyback transformer.

I have replaced C166, C167, and C114. R204 measured 40% high so it will get replaced. Also R212 & R214 both measured high while R213 was open. The HV pot was turned all the way down which makes sense R212 & 214 measured high. Fixing this should help to adjust the HV within range. Once I get all of these parts replaced I will report back.

https://i.imgur.com/KPRhhKW.png

https://i.imgur.com/TiVAJuJ.png

Once you get those parts in I would recommend temporarily removing the HV cage door, running the set over 5 min in a very dimly lit room and trying to locate the exact point of the hiss. The hiss is probably corona (the HV discharge not the virus) or arcing. HV cages collect dirt like a magnet and dirt can be conductive. Cleaning with isopropyl (rubbing) alcohol and glass cleaner will help. Some sets had a rubber insulation tire on the flyback and those sometimes become somewhat conductive and have to be peeled off and replaced with sensor safe silicone...Shango66 on youtube has some good vids on the topic (on RCA CTC17 sets IIRC).

EDIT: I'd also measure the 1000V and 800V boost supplies. Knowing if they are below (excessive load on flyback or insufficient drive), within 10% of rated( normal), or high (under loaded or overdriven) as well as control and screen grid voltages on the output tube usually gives a pretty accurate picture of where in the horizontal circuit the problem(s) lurk.
If your DMM can only read 600V (common limitation) you can get around it with this clever trick (came up with it on the spot while servicing a console in the owners home with limited equipment)...Connect meter neg to ground and measure a B+ rail in the 400-500V neighborhood and write down it's value, then connect meter negative to that B+rail you just checked and the positive meter terminal to B+ boost and add the noted value to your meter reading to get the actual boost voltage. The difference between a 450V rail and the 1KV boost rail is only 550V so a meter rated for 600V max can safely measure it.

First priority should be a good stable horizontal circuit, followed by focus, then anything needed to make the monochrome picture optimal, then fixing the color.

Nice save!
I was going to suggest looking inside the HV cage in darkness also.
If the HV is lower after replacing the parts you might have solved that breakdown/corona problem. If you use several cleaners in sequence you should end with alcohol, that will remove any left over moisture.
BTW, this is why only replacing the old tubes that test bad should be replaced. You could cook a brand new tube if there is a circuit fault.
You are making a big step going from radios to a color TV. This could be a long road. Do you have a color pattern generator? You may need one to adjust the convergence and color balance.
Fixing the HV first is a good call (assuming the main supply voltages are good), the regulation of the HV is important to get the image correct. In a B/W set small changes in the anode voltage don't effect the picture noticeably, but it does in a color set.

I love those PB sets! Built like a Zenith with a fold-out chassis, kind of the best of both worlds. I always thought they had very dowdy control panels though.

It would be interesting to know if the HO tube still redplates after replacing those two capacitors, and what the voltage is on pins 2-6.

I got parts in today and made several changes. Maybe not the best way to troubleshoot as it's hard to tell what change affected what, but see below for the changes made since the initial noted hissing, redplating on the horizontal output tube, and tripping the breaker:

Replaced the horizontal output tube as I am not sure of it's state now
Replaced the HV rectifier as it was glowing blue, i.e. a gassy tube
Replaced C166, C167, C114
Replaced R204
Replaced R212, R214, R213 with HV resistors and centered the HV adjust pot
Hooked up meters for testing


I installed the chassis and tried again but unfortunately tripped out the breaker. here are my notes:

At no time did the horizontal output tube glow red
I had the lights off several times while running and as the HV cage area started to hiss but I could not see any arcing
The horizontal output tube current first measured at 235ma so I turned down the horizontal efficiency to bring it just under 225ma
On the second try I remembered to hook up my DMM to measure the horizontal output grid voltage on pin 2 & 6, it measured at -56v while the schematic specs only -46v
On the second try the horizontal output tube current measured at about 125ma, I didn't make any adjustments this time so I am not sure why it was lower
HV measured at 24k volts on the first try and 23K volts on the second try
I let the set cool for 30 min and tried a third test, this time the horizontal output tube current measured approx 50ma but had -68v on the grid, adjusting the horizontal efficiency didn't affect anything so I turned the set off and am at a stopping point
I just now seen Tom's edit about checking the 1000V and 800V boost supplies so I will have to go back later and check these.


As for the picture after some fiddling with vertical control I could get a steady readable picture, it is still only B/W and blurry. I will have to look into why the horizontal output grid voltage is running 10+ volts too negative. Would this cause something to heat up, cause the high voltage hissing noise, and trip the breaker or would the symptoms point to a second issue to fix, I am open to your thoughts.

Attaching the horizontal multiplier circuit for further reference:
https://i.imgur.com/rAsO1y7.png

MULT here stands for multivibrator (oscillator).

So you definitely have drive. It is curious that it is giving a more negative grid voltage but it is a less dangerous issue than the grid being less negative.
Horizontal output screen grid(pins 1-7) and boost are important to know. If screen is high it means the flyback is drawing too much current, if it is low it means the flyback is drawing too little current (and cathode emission is being absorbed primarily by the screen grid which is bad for the tube).

When diagnosing horizontal knowing that the grid is not too positive tells you the osc is working, and the screen grid and boost voltages are the more important for troubleshooting.

If you can't see the hiss you could find it by ear...get a few feet of small plastic or rubber tube or hose. Hold one end of the hose to your ear and move the other one around in the HV cage like a stethoscope and listen for the loudest hiss.
Sometimes sets develop HV breakdown in strange places ...a friend brought me a tube color 13" Zenith once that the screw that held the HV rect socket to the insulator cup had arced through the bottom of the cup to the chassis. You couldn't see the arcing but it was loud enough to find. Had to drill out the carbon tracked plastic, fill it with silicone and shorten the screw to repair the issue.

I have had a very busy weekend so far. One exiting thing was I found a 1969 Packard Bell parts TV. This was a top of the line TV/Stereo console set, model CP 984. The TV is non-working, some examination shows a burnt wire in the yoke coil. It has a different chassis with a lower tube count (more solid state components) but does share some common parts to include the fly back transformer which had been replaced at some point.

https://i.imgur.com/gOt0G6T.jpg?1

I also had found on eBay NOS high voltage sockets for the high voltage rectifier & focus rectifier tubes and plate caps with 30K wire for the horizontal output and shunt regulator tubes. I thought lets eliminate all sources of possible HV leaking. Finally I picked up some additional meters for testing. While the chassis was on the bench I did jumper the circuit break to test. I used a variac hooked up to a hair dryer and found that slowly turning up the voltage the breaker trips at about 3.5 amps.

So after installing a different flyback transformer, sockets, and plate caps with associated HV wire I got the chassis back inside the TV along with lots of meters to monitor things, here are my testing notes:


TV draws 2.8 amps from the AC line
Horizontal output current dialed in at 220ma
HV adjusted to 23K volts
Reading -51 volts on the horizontal output tube grid vs -46 per the schematic
0.850ma shunt regulator tube cathode current, spec states should be at or above 0.850ma
After about 5 min the shunt regulator tube cathode current started climbing up to at least 1.2ma, shortly after this I got visible/audible sparks from the shunt regulator tube plate cap, I then cut the power
I repeated this for a second time, all measured good and again the shunt regulator tube cathode current started to climb, I believe I could start to hear some hiss so I turned off the TV
I feel like I either fixed one problem and now am on the next, or I increased the difficulty for HV to leak and now fails more visibility
At no point did the breaker trip, but I was watching and cut the power likely ahead of the breaker tripping

As I look at the shunt regulator circuit there are not too many parts. I have already replaced C114, but I just now measured R215 which calls for a 1000 ohms, 5% resistor. It measures high at 1,164 ohms (16% off), could this be the issue, or could it be further changing value as it heats up?

The other concerns it around the cap I used to replace C114, I was able to match the temp code from one of the replacement parts noted from the SAMS document so I hope I am ok here.

A resistor that is changing value may very well be the problem.
To bad you didn't monitor the HV during the time the shunt tube current was rising. Voltage breakdown at the cap would point to the HV moving higher.
I don't see that you said that you replaced the shunt regulator tube, that may be another possibility.
Kind of odd that the shunt current rises yet the HV is still climbing.
Sounds like the flyback is over producing.

Update: I finished replacing resistors and capacitors that measured bad in the horizontal and high voltage circuits. I have replaced all of the high voltage tube sockets as there may have been a possible HV shorting issue. I also added a 250ma fuse to the horizontal output tube.

The TV starts up, I get audio and the screen lights up but as before the horizontal output tube current slowly rises and eventually pops the fuse. I tried several times to fiddle with the horizontal hold and horizontal efficiency but in all cases I could not get the picture to hold and eventually the horizontal output fuse would blow. The HV does rise starting at 23k volts up to about 25k volts before the fuse blows.

Any ideas or what to check next for why the horizontal output current rises?

Voltage measurements:

23-25k HV source set and initially measured 23k volts
390v source measured 409 volts
275v source measured 312 volts
1000 boost measured 871 volts
810v boost measured 819 volts
-46v Horizontal Output tube grid (pin 2,6) measures -50.6 volts


TV image:
https://i.imgur.com/OfZ1fqV.jpg

If the horizontal frequency is running lower and lower with time, that could raise the current draw.
I would work on getting the horizontal sync good first.

I missed whether you checked X14 (dual diode AFC detector) or not.

Do you have a scope to check waveforms vs. the schematic?

If the horizontal frequency is running lower and lower with time, that could raise the current draw.
I would work on getting the horizontal sync good first.

I missed whether you checked X14 (dual diode AFC detector) or not.

Do you have a scope to check waveforms vs. the schematic?

+1
A horizontal osc running reliably on the correct frequency to achieve sync is the key stone of the horizontal opperation... without that you will end up chasing your tail trying to solve problems the Osc causes elsewhere.

I'm also a bit suspicious about that 1k boost..

I am not sure what exact part fixed the rising horizontal output tube current but a combination of the following let me run the TV for 30 min, after which I turned it off. Here is what I fixed:

Replaced all of the parts from the horizontal osc. plate to the horizontal output grid
Replaced the horizontal osc tube with a NOS tested tube
Replaced the boost rectifier and C119 capacitor which brought up the 1000v boost to a measured 1020 volts, thank you Zeno, I did use a NOS ECG 119 selenium rectifier
Replaced the horizontal AFC diodes
Replaced the remaining film capacitors located on the bottom chassis, note I still need to go through the other circuits

One remaining concern - the horizontal sweep circuit adjustment recommended adjusting the horizontal efficiency coil to keep the horizontal output tube current under 225ma. When adjusting the horizonal hold to get a stable picture the horizontal output tube current ran at 240ma. Are there other settings or other parts to check so I can bring the current down. I suspect the horizontal output tube and flyback transformer will not like running hot long term.

NES source, playing Legend of Zelda:
https://i.imgur.com/DF6OG68.jpg

The trouble is this set has something thats just off. Odds are
its not a wide open resistor or dead shorted cap. If you have
a scope look at the drive. Should be one ( or 2) BIG spike
& otherwise clean.
One thing that gets missed is the hoz blanking tube. That can cause some
strange problems. Change it & check around that area. It may be transtorised
also.

73 Zeno:smoke:
LFOD !

More measuring and also fired up my new Tek scope. The best part of a project is getting to acquire new tools:

AC line voltage 123 volts
390v source measured 405 volts
275v source measured 294 volts
Horizontal output grid 2,6 spec -46v measured -43v volts
Horizontal output grid 2,6 spec less than 225ma. The best I could adjust for was 240ma current at 24k high voltage
Horizontal output grid 1,7 spec 130v measured 130 volts
Horizontal output grid 8 spec 37v measured 42 volts
Horizontal output grid 2,6 drive. Scope setting 50v per division, 10us per division
https://i.imgur.com/siHqKOu.jpg?2
https://i.imgur.com/RFE3eSy.png?1


Zeno, thanks again for your advice, the horizontal blanking amp is a 6GH8A. Other than replacing all of the electrolytic caps on this set I have not checked any parts in this circuit or other remaining circuits.

Been working on a home improvement project so not much progress but I did pick up a Sencore CR70 and was able to test the 2 CRTs I have. Both are Packard Bell labeled 25xp22 which makes me think they are original to the TVs.

Naturally the tube in my project TV has no cataract or discoloration but measured almost no cutoff on red or green and barely any for blue. Emission is very poor for red, marginal on green, and fair on blue.

Now the CRT out of the large parts console I picked up measures good all around but it is quite discolored under the safety glass. I have watched shango066 pull off the safety glass on several CRTs so I see it is possible. What does everyone think for this one? Also let me know if anyone has a CRT they want to sell and ship to me (I will post a separate thread in the classified section).

https://i.imgur.com/LESkWYe.jpg?1
https://i.imgur.com/baDiFf0.jpg?1
https://i.imgur.com/3kvPFow.jpg?1

Been working on a home improvement project so not much progress but I did pick up a Sencore CR70 and was able to test the 2 CRTs I have. Both are Packard Bell labeled 25xp22 which makes me think they are original to the TVs.

Naturally the tube in my project TV has no cataract or discoloration but measured almost no cutoff on red or green and barely any for blue. Emission is very poor for red, marginal on green, and fair on blue.

Now the CRT out of the large parts console I picked up measures good all around but it is quite discolored under the safety glass. I have watched shango066 pull off the safety glass on several CRTs so I see it is possible. What does everyone think for this one? Also let me know if anyone has a CRT they want to sell and ship to me (I will post a separate thread in the classified section).

https://i.imgur.com/LESkWYe.jpg?1
https://i.imgur.com/baDiFf0.jpg?1
https://i.imgur.com/3kvPFow.jpg?1
That CRT shown is a Zenith/Rauland sourced CRT, with the famous halo.
There's a few entries on this forum dealing with this. It's an easy fix.

The Zenith style cataracts (green halo) are easy to fix. With the tube removed from the cabinet laying face up peel the tape off the edge, then take a number 18 steel guitar string* and securely affix each end to it's own wood handle. Hold the wire tight with a handle on each hand and press it firmly into the glue while sliding the wire along the glue to saw through. I typically start at a corner, and get the wire in along one side of the rectangle and cut towards the other side (instead of going top of screen to bottom). The glue sawing usually takes less than 10min once you get a feel for it. Once the wire is running down a side it typically has a LOT of resistance so I pull one handle with both hands till the other handle has an 1-3" of wire separating it from the glass then, I switch to pulling that handle and repeat. The tube doesn't have to be warmer than room temperature for this...I've done this on tubes in 45 degree weather at night and had it go well.
Once the glass is off peel the glue by hand (use an old credit card if it's stubborn) and clean residue with Goof Off then glass cleaner, then use 1/4" foam double stick tape spacers in the middle of the 4 sides of the screen and caulk the safety glass back on. Don't caulk more than 1/4" in from the edge of it may be visible in the cabinet, and let it dry the full 24 hours before reinstalling or putting weight on the safety glass.
Before you caulk make sure the CRT face and safety glass are spotless cause you don't want to have to open it to clean it once it's caulked.

*I've been using smooth guitar string but some folks have suggested using the bumpy stuff might improve the sawing action...I worry the bumpy wire may scratch the glass and or make the handles too hard to pull (they are enough of a work out with smooth wire). I haven't tried the bumpy wire or heard of anyone using it so I can't say if it changes anything in practice.

If you come over here when the weather gets above 50 degrees I'd be happy to do the cataract removal for you.

New update - I got some time to check components in the color circuits. Film capacitors and out of spec resistors all got replaced. There were a few resistors over 30+% but I suspect the issue was an open resistor that connected +275v to part of the 3.58 osc circuit. Other work included replacing the circuit breaker with a fuse and wiring in a bucking transformer to bring the line voltage down.

I picked up a RF modulator so I could connect a DVD player. With some basic adjustment I was able to get the picture reasonably centered, not much for color as I previously noted the CRT is weak. I continued to monitor the horizontal output tube current, I was able to get it down to a steady 210ma.

Next up:

Swap out CRT, and make applicable adjustments
Clean tuner, it seemed like I could maybe get a bit better picture and sound as I adjusted the fine tuning
Figure out what is causing the visible retrace lines


https://i.imgur.com/ejK46yJ.jpg?2
https://i.imgur.com/czvh9F4.jpg?1
https://i.imgur.com/QOgHvFP.jpg?1

That TV looks amazing! A fully vacuum tube high voltage power supply is cool to see in a color TV. Those shunt regulator tubes emit soft x-rays. The high voltage cage doesn’t just block accidental arcing. It also blocks the x-rays. Even without the cage, the x-rays probably can’t travel more than a few inches thru the air.

I currently have a dozen CRT TVs, but only one non-solid state TV. It uses semiconductor diodes in the flyback power supply. I am looking to see expand my non-solid state collection. The circuit designs are more beautiful when they are only tubes.

I'm not familiar with the rectangular Packard Bell sets, but most sets tend to take the retrace blanking off the plate of the vertical output tube. The components that couple that into the video chain need to be good, and the screens, drives, bias, brightness all need to be adjusted properly. Even a perfectly working set can produce retrace lines if adjustments are wrong.

After some further repairs I am questioning how well the RF/IF sections are working. My thought was to splice in composite signals to see what the set can look like.

I found a few posts with various ideas along with a few points of caution such as transformer isolation, inverted phase signal, and signal strength mismatch. It is not clear to me where I would splice in composite video. My first thought might be at the video detector diode cathode (X9). I am confused around if there is signal that is needed ahead of the pulse gate diode (X11) as this feeds the horizontal output tx and deflection circuit.

Next post has the relevant portion of the schematic.

https://i.imgur.com/VVd3DvE.png

If your set has a power transformer (and is not hot chassis) you don't need an isolation transformer.

It looks like sync is peeled off the emitter of the video amp so the only place you CAN inject without loosing sync is between the detector diode and the base of the video amp.

If polarity or amplitude is wrong you'll need to build an external video amp to fix that.

X11 does not feed the horizontal deflection circuit. The horizontal deflection circuit feeds X11 and Q6 to develop the AGC voltage. (X11 protects Q6 from the negative part of the pulse waveform). So, no modification is needed here.

You need to connect inverted video to point B (base of Q4). The average DC of the inverted video should match the 7.5 volts shown on the schematic. The part of schematic you posted doesn't show what the peak to peak video should be. Does your service info show a waveform for point B?

old_tv_nut and Electronic M, thank you for the replies. The set is a power tx set so no need for isolation and it sounds like I will need an inverted signal.

I found an old post from you with a circuit design. I understand I can adjust the collector resistor to change the output, also can I skip the .22uf on the collector as I am feeding directly into Q4? Additionally read that a clean 12v is important. I have 19v on the board to work with so I could add a voltage regulator to drop down to 12v. Some quick searching suggests this transistor should work: https://www.digikey.com/en/products/detail/onsemi/2N4401TA/3478153

As for details on the waveform I tried to clean up and shrink the schematic to better fit. See below from Sams which includes the waveform, also posted is the inverter/amp circuit.

https://i.imgur.com/v3XRTDx.png
https://i.imgur.com/Ziw9H2n.png

My first try would be:
Disconnect L8.
Connect the collector of the inverting amplifier directly to base of Q4 (don't use the 0.22 uF.)
Add 330k across the 33k in the inverting amplifier to bring the collector voltage down slightly, closer to the schematic voltage for point B.

I will give this a try and report back. Would there be any noise coming from the AGC keying or Noise Inv circuits (Q6 & Q7). Would it be helpful to disconnect these from where they tie into the sync amp?

I will give this a try and report back. Would there be any noise coming from the AGC keying or Noise Inv circuits (Q6 & Q7). Would it be helpful to disconnect these from where they tie into the sync amp?

They also are being driven by the video, not the other way around, so I think they are OK. I would try the amp without disconnecting them, and see if there is a problem. If everything works, you have saved some unnecessary work.
If you do have a problem with pulses feeding back, then of course you can disconnect them at that time.

A few comments.
1) the CRT tags look like Rauland ( EIA 1101 ) or Zenith ( EIA 343 )
Zenith owned Rauland. They bought them in the early 50's to assure good access to CRT's. Known to be very hi Q jugs.
2) blue screen w/retrace most likely blue G-2 is too high or one of the other blue gun voltages is way off. Turn blue G-2 down til the lines go away & see
if it gets better. Actual blanking problems are not common.
3) tuner / IF. Take signal off set. You should get very nice snow & a "waterfall" from the sound. If not we can dig in further.
good luck
Zeno:smoke:
LFOD ! & that goes especially for the Ukraine !

\After some further repairs I am questioning how well the RF/IF sections are working. My thought was to splice in composite signals to see what the set can look like.

I found a few posts with various ideas along with a few points of caution such as transformer isolation, inverted phase signal, and signal strength mismatch. It is not clear to me where I would splice in composite video. My first thought might be at the video detector diode cathode (X9). I am confused around if there is signal that is needed ahead of the pulse gate diode (X11) as this feeds the horizontal output tx and deflection circuit.

Next post has the relevant portion of the schematic.

Who manufactured the picture tube?

For this set I scored big and picked up a NOS Zenith 23VCMP22.

I did keep the old CRT but have not attempted to remove the cataract, it looks like a Rauland 1101 EIA code from my earlier picture.

https://i.imgur.com/bVJwAoe.jpg?1

Oh that is a SWEET Packard Bell set, what a score!

I built the composite video injection and it is working, kind of. A few notes and questions.

I pulled power from the 18v supply off the IF/video/audio pcb board. Normal (stock) operations it measures 17.5 volts. For the composite video injection circuit I included a 12 power regulator to get a regulated 12 volts. I was surprised to see the IF/video/audio pcb board voltage pulled down to 15 volts. Is there any reason I cant provide an external 12 volts to power the composite video circuit and avoid tapping into the "onboard" power?
I grounded the circuit to "chassis" ground via a ground test pin on the IF/video/audio pcb board. If I use an external 12 volt supply are there any grounding concerns I should be aware of?
I used a pot for now to temporarily adjust the video signal voltage. The normal video signal measures 7.5 volts and I was able to adjust the gain to match. I couldn't make full sense of my scope, I expected to see that same signal voltage but there was a difference. Am I just looking at noise, see below pics.
The injected video required tweaking of the horizontal and vertical hold to get a stable picture but depending on the input (DVD vs converter box) the picture just didn't look right. Further I have (what I think is an unrelated) bad convergence problems which makes it difficult to gauge how well this composite video injection circuit is working. Any thoughts would be helpful, pending no changes suggested I may put it all back and dive in for some help with convergence.


Original video feed
https://i.imgur.com/oPvl5Dh.jpg?1

Composite injection
https://i.imgur.com/NaL5lnb.jpg?1

1) yes, you can use an external 12 volt supply.
1b) post a schematic of your circuit - it may be drawing more current than necessary depending on the resistor/pot values you used.

2) When you say you adjusted the amplifier to match the internal signal, is that a DC voltage reading of 7.5 volts? You need also to match the peak-to-peak voltage, and your waveforms look like the injected signal is much smaller.

3) the internal signal has much bigger sync than the injected one - your amplifier may be clipping sync. It would be good to buy a DVD with test signals like color bars that have known video levels instead of looking at program material where the video level varies scene-to-scene.

I spent too many hours working on the color setup and convergence, but for now is acceptable. Back to the video composite injection circuit see below for the video signal when viewing a test signal. The video wave form shows about 10v pp. I should note the TV picture is using the tuner, I have removed the injection circuit for now.

Work in progress:
https://i.imgur.com/LbzOLzy.jpg?1

Video signal from above input using the tuner:
https://i.imgur.com/KdNaif5.jpg?1

Here is the circuit I used for the injection:
https://i.imgur.com/pCshVsG.jpg?2

I'm surprised that the detector output is that large, 10 Vpp. I was guessing something more like 4-5 v p-p.

The injection amplifier has a gain of 4.7x, so will only have 4.7 v p-p out. You can increase the gain by making the 470 ohm emitter resistor smaller, but it will be hard to get a 10 v pp signal out with a 12 volt supply. Your pot will have to be adjusted carefully, and because of the AC coupling, the DC will drift up and down with scene content, clipping whites in a dark scene or sync in a bright scene. To keep things stable, you will need a DC restorer.

The input of this amplifier shows how you could add DC restoration:
https://www.eleccircuit.com/video-amplifier-splitter/

Ok I am bouncing between tinkering with adding a composite input and also still trying to dial in the color purity and convergence.

I am redoing the color purity and I am struggling to get an all red picture, note it has never been perfect yet. Is getting perfect color purity all a matter of mechanical adjustments of the yoke and convergence magnets? I can get an all red picture but the centering is way off. What else should I look for?

One other thing is I can get the purity better by playing with the horizontal hold which I guess moves moves an uncentered red screen back to center but then on restart the picture could not hold until I adjusted the horizontal back.

Also note the above purity adjustments I am trying are with the tuner, I have paused on the composite input for a bit.

... I can get an all red picture but the centering is way off. What else should I look for?

One other thing is I can get the purity better by playing with the horizontal hold

Horizontal hold should not affect purity. You may be seeing the effect of mistiming the burst gate. Set H hold to mid range and leave it there.

Strong interaction of the purity rings and centering may mean the rings are at the wrong position on the tube neck. Look for an illustration of the tube neck components and try to match it.

Hard to give advice without being there to see what you're doing.

Are you using an all-red video, or killing the green and blue guns? A video could produce an impure red if the tint/hue control is not set perfectly. Killing the green and blue guns by grounding the G1s is the best way to be sure only the red gun is emitting.

I am using an all red signal via a setup DVD and then turning the blue and green guns all the way down.

... turning the blue and green guns all the way down.

That should be good.

I am using an all red signal via a setup DVD and then turning the blue and green guns all the way down.

Be sure purity rings are at the REAR.
Warm up set 1/2 hour.
Degaus CRT.
Slide yoke BACK.
Turn color all the way down & turn OFF any auto color switch.
WITHOUT signal turn down the G & B screen controls.
Turn UP the red g-2 til retrace lines then back off til they go away
Now you should have a red blob apx the center of screen.
Center the blob.
Slowly push yoke forward til the whole screen is RED.
Too far & you will loose the purity again.

NOTE unless you are short, to make these adjustments its MUCH easier
to lay across the set. Mirrors are a PIA & not as accurate.

73 Zeno:smoke:

Make sure you have the purity ring set for minimum effect to start. Can you post a pic of the components on the neck as they are currently?

When Zeno wrote "center the blob" that meant center the red blob by using the purity rings, not by using centering controls.

My apologies for the delayed reply, I completely missed seeing the replies here on page 4.

Ok so I am feeding in composite video from a DVD player into my RF converter. The feed is from a DVD titled TV Test Card/Video Pattern Generator DV. I have the green and blue screens turned down and am using the all red signal from the DVD player, note the video has a black + in the center and white arrows on each side.

See below for the results. I would say it is a bit better than I had before but I can not get the image centered nor does it completely fill the screen. If I try to center the image I can not get to an all red purity.

Note I can move the image over via the horizontal hold but then when I restart the TV the horizontal hold is lost and I have to bring it back to off center.

Let me know what you think, also if more pictures or a video would be helpful.

https://i.imgur.com/96ekb7X.jpg?1
https://i.imgur.com/gI41MUf.jpg?1
https://i.imgur.com/sLefxdD.jpg?1

More questions:

Did you take a picture of the position of all the neck components before replacing the picture tube?

Is the white device between the purity rings and the convergence yoke the centering control?

I did take some pictures before removing the old crt, see below for how the purity was adjusted. As for the installation I have the yoke, then the red/green/blue convergence assembly, and then the the blue lateral and purity control which is one part. Am I missing or forgot something?

I have been trying to both center the screen and get color purity by adjusting the purity magnets and sliding the yoke forward and back. Note sliding blue lateral and purity control forward and back provide some very minor effect.

https://i.imgur.com/Msgen9d.jpg?1

...and then the the blue lateral and purity control which is one part. Am I missing or forgot something?
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Um.. aren't the purity rings supposed to be located forward (front-ward) of the blue lateral? Might try reversing the assembly.

Nope rings are last on.

I was thinking blue lateral after I posted. It seems a peculiar design to have it attached to the purity rings and not the convergence assembly, but it is what it is.

When you adjust H centering, how are you doing it? Is there a centering control, or are you trying to fiddle with the yoke? Some sets (like my old Magnavox roundy) had no centering control and you just had to take what you got. The H sweep was wide enough to avoid black edges, but you could lose up to 20% or so of the picture.

As yours is not filling the screen, the problem may involve the H output, H drive/efficiency/linearity adjustment, H driver, etc.

old_tv_nut, thanks for the replies. It seems that I may have to compromise on color purity or centering. There is no specific centering control as I understand.

I can move the screen left to get it centered with the horizontal hold but then when I turn the TV off and back on the horizontal hold is lost. I will try again and see if I can find a combination of horizontal hold & horizontal efficiency that allows me to fill the screen and have good color purity. Are there any key component values that I could check or even change to provide some further range?

Is there an interaction with the vertical linearity, vertical hold, and height? Also there are controls for the pincushion amp, and pincushion phase, note Sams states the pincushion phase is factory set and seldom needs adjustment.

Compromising purity for anything else is not possible; you can only make it worse. So set the yoke and purity rings for best purity, and leave them there.
Don't use horizontal hold to adjust centering. This will affect the timing of the color burst gate and potentially make color unstable. Horizontal hold should be set to the center of the hold range.
Consult SAMS on adjustments in the horizontal sweep section. Note that any horizontal efficiency adjustment must be set so that the horizontal output tube doesn't draw excess current.
Use an Indianhead or similar test pattern with circles to check width and linearity. Use a crosshatch pattern to check pincushion amplitude.
Vertical and horizontal adjustments are generally independent of each other.
SAMS should give an indication of what order to do these various adjustments.

Your width problem could be due to weak tubes in the H sweep section (H driver, H output, damper).

Good luck!

Still fighting this set. After lots of attempts at getting the purity and convergence setup correctly I can get good color purity but am unable to get the picture to have good horizontal centering, I am left with unused screen on the right side. I can use the centering rings to center the screen but then cant get good color purity. I have checked the B+ and boost voltages all measure good also tried swapping the horizontal output and damper tubes but seen no improvement. This suggests that the issue is not a width problem.

In looking back at pictures the centering issue was not present before I swapped out the CRT, now to be fair I had not checked for purity on the old CRT so the issue may have been there, still could it be the new CRT? Also since installing the new CRT I ran into an issue with HOT high current, it was an intermit resistor that would measure ok on the bench but fail in operation. I resorted to shotgunning lots of parts, while I have checked and rechecked all part values I certainly could have made a mistake somewhere. Thoughts on any key components I should check that would allow the set to operate well but not have horizontal centering.

Full PDF Schematic: https://drive.google.com/file/d/1FdaMUSUQ0-5s-ilhvof0QokLMrdijFeG/view?usp=sharing


I was browsing schematics and it looks like earlier RCA sets did have horizontal centering via a 10 ohm pot across taps on the flyback which then feed the yoke. Maybe something can be hacked in but I'm not up to that without good guidance.
https://i.imgur.com/oPZscVd.png.

I lost track of what all was tried in this thread.
Is the raster actually off center (no light in the black part if you turn up the brightness) or could the horizontal phase be off (raster is centered but the picture is phased to one side, black part of the screen lights up when you turn up brightness)?

Looking closely at your blue lateral magnet it looks like the wheel you turn should be at 12:00 and not where you have it currently. The blue gun is the top gun in the neck of the tube. I remember on Zenith lateral magnets that the rotating adjustment part was at the top of the neck on the jug.

old_tv_nut to you question, I don't know, I was thinking that the raster was shifted to the left. During setup it seemed that the raster as a whole was being moved to the left via the purity rings to get an all red screen. But maybe the right edge is just missing the picture and still receiving a black raster.
https://i.imgur.com/nQywj55.jpg?1

See the below video where I turned the brightness up and down, the image curves in as the brightness goes up. I can get the right edge of the screen to light up but I don't know is this raster or just light shining through?

Short Video: https://imgur.com/ZPrGLCY

old_tv_nut to you question, I don't know, I was thinking that the raster was shifted to the left. During setup it seemed that the raster as a whole was being moved to the left via the purity rings to get an all red screen. But maybe the right edge is just missing the picture and still receiving a black raster.
https://i.imgur.com/nQywj55.jpg?1

See the below video where I turned the brightness up and down, the image curves in as the brightness goes up. I can get the right edge of the screen to light up but I don't know is this raster or just light shining through?

Short Video: https://imgur.com/ZPrGLCY

Just turn the brightness to max and you'll see if that area lights.

Edit: I didn't see the text below the picture at first.
It looks like there is a little bright strip on the right side and then full balck (no raster) (?)
If that is correct, the problem is not horizontal phase but raster shape and centering as you have been saying.

Second edit: Sorry i'm not awake! I looked at the video now and it's obvious the raster goes all the way to the right edge of the tube (and probably beyond) as the whole area lights up.
Once again, you need to go for best purity first and not change that, then see if you get the same effect (light all over the right side when you turn up brightness, but picture pulling to the left.) You may have two problems at once and need to not try fixing one by adjusting the other.

If the horizontal sync phase is the problem, suspect the phase detector X14 and the components around it.

If your scope is dual-trace, connect one probe to X11 (AGC gating pulse) and the other probe to the video detector output and see if the pulses line up and don't move with respect to each other with changes in video content etc. Make sure your scope is triggering on channel 1 only or channel 2 only.

also make sure X11 is good

old_tv_nut, thank you for the troubleshooting ideas, I am way into uncharted territory. I will start with checking components around X14 and X11. I do have a 2 channel scope but will have to pick up a second probe. Stay tuned and thanks again everyone for the advice.

In looking at replacement parts Sams notes that X14 can be replaced with the following:

Sylvania ECG 113
General Electric 6GC1
International Rectifier DD04


Now in scanning Ebay I see both ECG 113 and ECG 133a, the descriptions states selenium and silicon respectively. Can I assume these are interchangeable and the silicon is likely the better choice?

https://i.imgur.com/MZoSWDM.jpghttps://i.imgur.com/XPkRf4A.jpg

If I had stumbled fresh onto seeing the screen shot in post# 60, the first thought woulda been "borderline-weak H output tube". And the first move would have been the "7 seconds off" test. That is, with the set running, turn it off for about 7 seconds, and back on. If the width is slow to fill back out, the tube may be borderline ('specially if it's been red-plating much). Whereas if the width comes back quick, the tube is obviously good.

It's a 'quick & dirty' little test that can also show up other borderline tubes. E.g., H oscillator, color oscillator, vert output, RF amp.

In looking at replacement parts Sams notes that X14 can be replaced with the following:

Sylvania ECG 113
General Electric 6GC1
International Rectifier DD04


Now in scanning Ebay I see both ECG 113 and ECG 133a, the descriptions states selenium and silicon respectively. Can I assume these are interchangeable and the silicon is likely the better choice?

https://i.imgur.com/MZoSWDM.jpghttps://i.imgur.com/XPkRf4A.jpg

Nowadays shottkey is the best choice followed by silicon...garden variety 1N4007s (you'll need 2) are usable, but shottkeys will work better.

If I had stumbled fresh onto seeing the screen shot in post# 60, the first thought woulda been "borderline-weak H output tube". And the first move would have been the "7 seconds off" test. That is, with the set running, turn it off for about 7 seconds, and back on. If the width is slow to fill back out, the tube may be borderline ('specially if it's been red-plating much). Whereas if the width comes back quick, the tube is obviously good.

It's a 'quick & dirty' little test that can also show up other borderline tubes. E.g., H oscillator, color oscillator, vert output, RF amp.

Yes, this could be it.

A circular test pattern like the Indianhead would show the bad horizontal linearity in this case (compression on the extreme right), but you might also be able to detect it with a crosshatch.

I just looked up 6LQ6 prices online - YIKES. Audiophiles have jacked the market up out of sight.

So early in my repairs I replaced the horizontal output tube and damper tube with what eBay claimed to be NOS tubes, plus the sellers noted they tested good too (vs just looking NOS). A few weeks ago I picked up spare tubes and swapped these out but did not see any improvement. I don’t have a tube tester so who knows, I could have bought weak tubes.

and yes, silly expensive.

We ran into quite a few borderline width cases always on rectangulars, using brand new H.out and damper tubes. Had to finally resort to putting a 82pf, 6KV disc ceramic cap across the damper (cathode to plate). This bumps the width out just a smidjin. Sometimes had to increase to 100 or 120 pf to get 'just enough' overscan.

The mod also has the effect of lowering H.out cathode current slightly (good). But it also reduces HV slightly, requiring bumping the HV adjust up a bit. So there's no 'free lunch'. The usable value for that cap is no higher than 120 pf.

Assume something like this should hold up to replace the horizontal AFC dual diodes: https://www.mouser.com/ProductDetail/Vishay-General-Semiconductor/SB3H100-E3-54?qs=u91jd7aysvP%252BosR3IQl24Q%3D%3D

Schottky Diode
3 amp
100 volt