View Full Version : My First Predicta


Chris K
02-27-2023, 06:43 AM
I've successfully restored 2 Seventeeners that have similar guts but this is my first purchase of a Predicta. They don't come up for sale too often in my area. Holiday model in mahogany. Cabinet looks in good shape but the safety "plastic" looks pretty cigarette tar stained. I'll be picking it up this Saturday. I don't know the status of the CRT but that doesn't matter to me. I'll get a decent one from somewhere.

Chris K
03-04-2023, 05:23 PM
First hurdle. 21EAP4 tests strong at 2.4 volts with good cutoff. Happiness!

old_coot88
03-04-2023, 08:05 PM
Could the seller have rejuvvied it before selling the set? Finding one of those jugs that's not flat is a rarity.

Chris K
03-04-2023, 10:34 PM
I don’t think so. He was not an electronics guy. Had the tv for a month after finding it cleaning out a house.

Chris K
03-06-2023, 03:43 PM
Flyback looks to be in good shape. Chassis is almost all factory except for a capacitor on the main circuit board and the fusible resistor has been bypassed. Pretty clean and looks like it's had modestly light use. If Bob A is out there, do you know of a resistor substitute for the fuse plugin?

Electronic M
03-06-2023, 04:59 PM
I typically sub a fuse of the same current rating and a resistor the same or higher resistance and power.
You can still sometimes find NOS fusistors. I've found if the one in the set is good it'll typically stay good unless I mess something up, so if I find a bad one and I have a good replacement NOS I'll use the NOS.

bandersen
03-06-2023, 05:12 PM
Ah, but what is the current rating of the original? It's not in the service info.

The only thing I've ever found is this which rates them in wattage - not current. I assume 5.6 ohms at 5.6 watts translates to 1A. I've measured the B+ current in a few sets and it's slightly over 1A.

Watch this for suggestions on replacing them: https://youtu.be/hYDJZvHPM1A

https://live.staticflickr.com/65535/52731310008_b24b92b818_z.jpg (https://flic.kr/p/2okFKko)

Chris K
03-06-2023, 06:01 PM
Got it...thanks Bob and Tom. I can't find the startup thermistor on this one though. They're usually on the bottom of the chassis right? Hmmmmm.

bandersen
03-06-2023, 06:50 PM
Probably fell out. It happens a lot

Chris K
03-06-2023, 07:50 PM
You gotta hand it to Mr Rigotti. These are fantastic and a wonderful timesaver.

Chris K
03-15-2023, 09:15 AM
Got the shell and safety plastic off the CRT. I think the condition of the yoke provides more evidence this is a low hour TV. Nothing looking burned or full of dust...electrical tape still soft and adhered...plastic cover on the back of the yoke still pliable and no heat damage etc. Even though the glue on the label failed, the label itself is perfect and still glossy. The dag is perfect. I'm starting to believe more and more the CRT test on the Sencore showing strong emission with good cutoff is real.

At this point, there's no HV so the next step is to investigate that.

Chris

Chris K
03-15-2023, 09:31 AM
Some photos of the neck and its insides.

Electronic M
03-15-2023, 09:31 AM
For no HV check power supply is good, H osc is working (look for sufficient negative grid bias on the output), make sure the paper caps in the horizontal are changed and that the width pot isn't open (or dirty enough to act open), and make sure the damper tube is okay. Once those are checked good if still no HV lift the HV rect top cap and try to draw an arc from it....If you get a healthy arc then the rect tube is bad, it's heater winding/heater limiting resistor is bad (open or shorted to ground) or the wire from the HV rect socket to the CRT is open or unplugged.

If no arc anywhere after all that report the control and screen grid voltages on the H output tube vs schematic. Screen grid voltage will tell you if the flyback is drawing power from the flyback and if it's got a partial short or open.

Chris K
03-15-2023, 09:42 AM
Thank you Tom! Will investigate as per your flow chart this evening and will report back!

bandersen
03-15-2023, 09:46 AM
What about the rest of the set? Are you getting anything out of the speaker? Can you tune a station in?

Chris K
03-15-2023, 11:58 AM
What about the rest of the set? Are you getting anything out of the speaker? Can you tune a station in?

There is some static from the speaker but no change when the channel is changed. All tubes are lit.

Chris K
03-15-2023, 12:43 PM
Oh and Bob, it's been completely recapped...all electrolytics cut out and replaced with Nichicon caps and all waxies replaced. I installed new couplates from Mr. Rigotti's website. I guess I need to consider the possibility the TV suffered some sort of catastrophic failure, like a flyback short, early on in its use and was put away. That may account for what looks like, to me, minimal use.

The safety "glass" is another issue. The inside had the well described white powder residue. I've been using some fine automotive polishing compound and an electric buffing pad and it seems to be working but with considerable effort. It smells bad. I don't know if that's a common thing. It's also pretty dark. Do they yellow with age as well? I do know some plastic yellowing reversal techniques using hydrogen peroxide and UV light that I have successfully used on old computer equipment and vintage games. I would want lots of opinions and advice before I take any steps like that.

Chris

Chris K
03-15-2023, 05:19 PM
I changed the 1B3 out of another set that works and replaced the one in the Predicta but no change. I've got all of the B+ voltages...all maybe 10% low due to the age of the rectifier diodes that I didn't change. I'll have to look at the schematic as I can't get to the bottom of the H Osc socket, The choke or the VOT is mounted right under the tube and I don't have a test socket so I can check the bias. The resistor between the HVR and the HV lead to the CRT is right on at 5.5K and the HV lead has continuity. I did find something interesting as one of the wires going into the yoke chassis plug had pulled out of the pin socket but that's probably something I did moving the chassis around. It's been repaired.

bandersen
03-15-2023, 05:47 PM
They used tined plastic - do NOT try to chemical treat it. I've worked on about 200 vintage TVs at this point and have never found a bad flyback so that's the last thing I'd consider.

Yes, they smell - it's the Tenite plastic Cleaning them exposes fresh material and it will smell worse for a while. I've had good luck with ScratchX and Novus #2 plastic polish.

As for the CRT looking pristine, that's great, but not that unusual because the plastic shell protects them from the environment.

If you're not hearing anything when you change channels, you have at least one other fault - maybe related to the lack of HV like something is off with the power supply.

I always recommend the easiest thing first. Grab an ohmmeter and go through the resistance chart published in Sams. No need for socket extenders or an isolation transformer.

Everytime I've made a wiring mistake, I found it very quickly with this method.

Chris K
03-15-2023, 05:58 PM
One thing that makes this hobby more difficult than it probably should be...I am significantly colorblind. Resistors and bumblebee capacitors are very difficult for me to interpret and I rely on Sams chassis pictures, what the installed capacitor is labeled as and the parts list. Below is the only capacitor in the main chassis that I have not replaced. I can't see it in the small Sams picture and I can't find it on the schematic. It reads a very weak .015 and leaks at 25 volts. Can I get some help?

Thanks
Chris

Chris K
03-15-2023, 06:01 PM
They used tined plastic - do NOT try to chemical treat it. I've worked on about 200 vintage TVs at this point and have never found a bad flyback so that's the last thing I'd consider.

Yes, they smell - it's the Tenite plastic Cleaning them exposes fresh material and it will smell worse for a while. I've had good luck with ScratchX and Novus #2 plastic polish.

As for the CRT looking pristine, that's great, but not that unusual because the plastic shell protects them from the environment.

If you're not hearing anything when you change channels, you have at least one other fault - maybe related to the lack of HV like something is off with the power supply.

I always recommend the easiest thing first. Grab an ohmmeter and go through the resistance chart published in Sams. No need for socket extenders or an isolation transformer.

Everytime I've made a wiring mistake, I found it very quickly with this method.

Thank you very much Bob. I'll check the resistance readings

Chris K
03-15-2023, 06:28 PM
OK there is an issue with the B+ voltages in 3 of the 6 DC sources. There is no 260v C source, the boost voltage is 225v (should be 435v) and the 140v source is reading 41v. Sorry about that. Looks like there is an issue!

bandersen
03-15-2023, 08:59 PM
That's a 0.01uF cap rated for 600v

Chris K
03-16-2023, 08:58 AM
They used tined plastic - do NOT try to chemical treat it. I've worked on about 200 vintage TVs at this point and have never found a bad flyback so that's the last thing I'd consider.

Yes, they smell - it's the Tenite plastic Cleaning them exposes fresh material and it will smell worse for a while. I've had good luck with ScratchX and Novus #2 plastic polish.

As for the CRT looking pristine, that's great, but not that unusual because the plastic shell protects them from the environment.

If you're not hearing anything when you change channels, you have at least one other fault - maybe related to the lack of HV like something is off with the power supply.

I always recommend the easiest thing first. Grab an ohmmeter and go through the resistance chart published in Sams. No need for socket extenders or an isolation transformer.

Everytime I've made a wiring mistake, I found it very quickly with this method.

Thanks for the information and the translation on the bumblebee capacitor! In my CRT evaluation, I was referring more to the heat damage I've seen on yokes after prolonged use. Just about every yoke on an almost dead CRT I've come across shows obvious signs of heat related degradation. Plastic warped and brittle...applied tape dried out and burned...wires with heat baked brittle insulation...discolored ceramic capacitors and resistors etc. Nothing of the sort on this one. Do damaged or dead 21EAP4s test as good sometimes? I really hope that's not the case with mine. It tested with good emissions and cutoff on my Sencore at 2.3V

bandersen
03-16-2023, 09:52 AM
Keep in mind the 21EAP4s have a design flaw that resulted in a short life - less than two years. Long before the issues you mention show up. For example, here's a dead 21EAP4 and yoke that look brand new.
https://live.staticflickr.com/65535/52750684957_2118d61651_z.jpg (https://flic.kr/p/2onp3Qe)

No, it would not test good if it had issues. I'm not saying all 21EAP4s are duds or doomed to early failure - just that that had a high failure rate initially. I replaced this dead EAP4 with another that tested like new. It had no label - so I don't know who made it though.

Yamamaya42
03-16-2023, 11:04 AM
I'm not sure which Predicta you have, nor have I had a chance to work on one yet, but they should be mostly alike, found this, so.

http://www.earlytelevision.org/pdf/philco_g4242_predicta_holiday_sams_439-1.pdf

Obviously the missing voltages are the first task.
No 140v = no IF, thus no video/ sound.
No 260v C will kill the horizontal oscillator/ HV, and thus you have no boost and it will be at low of 200v ish.

Looking at THIS schematic anyway, there has to be something really weird wrong for 260v C to be missing, without that, the cathode of the audio output will be all wrong, and thus 140v will be wrong as well.

Chris K
03-16-2023, 01:42 PM
I'm not sure which Predicta you have, nor have I had a chance to work on one yet, but they should be mostly alike, found this, so.

http://www.earlytelevision.org/pdf/philco_g4242_predicta_holiday_sams_439-1.pdf

Obviously the missing voltages are the first task.
No 140v = no IF, thus no video/ sound.
No 260v C will kill the horizontal oscillator/ HV, and thus you have no boost and it will be at low of 200v ish.

Looking at THIS schematic anyway, there has to be something really weird wrong for 260v C to be missing, without that, the cathode of the audio output will be all wrong, and thus 140v will be wrong as well.

That's the Sams I'm working from. I see what you're saying about Source C and the 140v. I'm not all that great with schematic symbols...is there anything significant to that X on the line between 260 B and 260 C line right next to the .047 capacitor designation? Could resistor R75, the 18K 2 watt be an issue? I'm going to replace the rectifier diodes anyway but I have 250 v DC coming out of them and not the 280-290 V that should be there.

Yamamaya42
03-16-2023, 03:23 PM
An x / broken line ( so on ) indicates an optional way of the circuit being wired, depending on run / make/ year / model.

Chris K
03-16-2023, 03:38 PM
Thank you...so if the model I'm working on does not have that jumper, could issues with the resistors I mentioned be a possible source of the lack of voltage on C and half the voltage on the 140v source?

bandersen
03-16-2023, 07:32 PM
+/-20% on the voltages is fine. They are very much dependent on your input line voltages and the operating points of all the circuits, condition of tubes etc.

Like I said, go through the resistance chart. There has to be a major smoking gun (or two) for voltages to be completely absent. It's not going to be something off be a few percent - it's going to be an open circuit or something shorted.

Chris K
03-16-2023, 08:38 PM
+/-20% on the voltages is fine. They are very much dependent on your input line voltages and the operating points of all the circuits, condition of tubes etc.

Like I said, go through the resistance chart. There has to be a major smoking gun (or two) for voltages to be completely absent. It's not going to be something off be a few percent - it's going to be an open circuit or something shorted.

I've started to. First I checked all the wiring from the AC line to the line filter cap, through the diodes, through the choke and the electrolytic caps that bracket it. It all checks out so that means I didn't screw up those first 3 electrolytics.

I started with V1, first tube in the chart and the first video IF tube, a 3BZ6. Pin one should be 1.5Mohm and I have that. Pin 2 should be 47 ohm and I have 65 ohm. Pin 3 should be 14 ohm and I have zero. Pin 4 should be 15 ohm and I have zero. Pin 5 should be 330 ohms measured from the 140v source and I have 420 ohm. Pin 6 is the same measurement parameters as 5 and I have the same 420 ohm. Pin 7 to ground should be zero and I have 0.1 ohm. Looking at the schematic, I don't see pins 3 and 4 connected to anything so I don't know what these mean. I really apologize asking you to take me by the hand but is there a tube in a different section I should check that would help figure this out faster?

Thanks Bob

bandersen
03-16-2023, 09:53 PM
3 & 4 are the tube filaments. I wouldn't worray about them since your tubes are lighting up. I suggest checking the 12CA5 audio output tube and the 12DQ6 horizontal output tube.

Chris K
03-16-2023, 10:13 PM
Oh of course they are. Duhhhhhh! Anyway thanks for the guidance. I’ll check back in to the board once I get more data tomorrow night

Yamamaya42
03-17-2023, 07:25 AM
Since it does not have the direct link as you mention for the 260V C, but through the unnamed 2.2k resistor ( current limiting? ) , doing as bandersen suggested should find the problem, be it a short or whatever, if it IS a short, the voltage drop across that 2.2k resistor would be rather large, and it's prob getting a bit warm!

Chris K
03-17-2023, 04:38 PM
3 & 4 are the tube filaments. I wouldn't worray about them since your tubes are lighting up. I suggest checking the 12CA5 audio output tube and the 12DQ6 horizontal output tube.

Happy Friday all and Happy Friday Bob!

I'll keep this simple. I'll state the tube and the readings will go from Pin 1 to the last pin sequentially. I won't give the pin number for clarity sake. I'll list the resistance readings as measured/should be. All were measured from chassis ground except where indicated otherwise.

12CA5: 96/68 0/480K 0/12 0/14 530K/480K 1100/1000 295/295

12DQ6: 0/0 12meg/22 0/0 192k/9k 1meg/1meg 500k/Tie Point 20/20 3/0 15/25 (Top Cap)

To me, the 260v C voltage isn't getting to the 12CA5...but I'm kinda lost! Any thoughts? I'll remeasure to be sure.

bandersen
03-17-2023, 05:39 PM
Well some of those readings are way off. I'd start by tracing out the 12CA5. Is pin 2 grounded accidentally? Pin 2 and 5 should be connected together so you should have gotten identical readings but you didn't?

Also check that the primary on the audio output transformer is good. That supplies the plate voltage to the 12CA5

Chris K
03-17-2023, 06:18 PM
Well some of those readings are way off. I'd start by tracing out the 12CA5. Is pin 2 grounded accidentally? Pin 2 and 5 should be connected together so you should have gotten identical readings but you didn't?

Also check that the primary on the audio output transformer is good. That supplies the plate voltage to the 12CA5

Audio output primary is good, 285 ohms. The reading on pin 2 is correct at zero. Checked several times. I thought I might get away with not removing the board but it's looking like I might need to.

Chris K
03-17-2023, 08:08 PM
So I pulled the board. At some point, the socket for the sync sep was replaced. Lousy job too. All the pins have continuity with the traces on the board except pin 2. In fact, the board is so discolored from flux and heat, I can't even see where it goes. In the schematic, pin 2 is the screen of the 9BR7 and it feeds into the K2 couplate. I do not have continuity between the pin 2 solder tab and the tab just to the right and above which would be the more likely candidate for continuity...again, the board is so fouled, I can't see if that's the case. No problem jumping the pin to another spot but I don't want to jump to the wrong spot. Anyone have any ideas?

bandersen
03-17-2023, 08:48 PM
That's the 10DE7. There is no connection to pin #2.

Chris K
03-18-2023, 08:12 AM
I better stop embarrassing myself and taking everyone's time. I'll dive into this over the next few days and see where I can get. Thanks everyone.

Chris K
03-20-2023, 06:30 AM
Sand resistor is all messed up. I cut it out and measured it. First section measuring 280 ohm...next two sections measuring in the 25-50k range. Final section is around 60 ohms. Have the appropriate 20 and 10 ohm high wattage wirewound resistors to replace. We'll see what happens.

Yamamaya42
03-20-2023, 07:42 AM
Are you referring to R77? Which seems to be the only multi power resistor in the set? ( 13/17/8 ohms?)

Or something else? If it's R77, then the heater string must be very starved of power!

bandersen
03-20-2023, 09:29 AM
Yeah, I'm surprised the tubes lit up at all.

Chris K
03-20-2023, 12:47 PM
Yep…R77 and those resistances

Chris K
03-20-2023, 12:54 PM
Well...let me make certain I'm measuring this correctly. Is it lug one to two for the first section and lugs two and 3 for the second section and so on or is it measured some other way?

Yamamaya42
03-20-2023, 01:07 PM
Section B ( what was between R76 tie point and tuner pin 4 wire ,also lamp m3) should be 13 ohms
Section A ( tie point and tuner pin 4 wire to tie point and tuner pin 3 / C53 ) should be 17 ohms
Section c ( tie point and tuner pin 3 / C53 to far point of part to filament strings) should be 8 ohms

anything way beyond this is big trouble :(

bandersen
03-20-2023, 04:26 PM
Yes, that is how it is measured

Chris K
03-20-2023, 04:41 PM
I replaced it like Bob's 2016 Flickr photo with 20 watt resistors at 15, 15 and 10 ohms. I remeasured the 9BR7 socket resistances. All in line except 4 and 5 both reading over 4 meg.

bandersen
03-20-2023, 08:15 PM
Those are the filament pins. You will only get a meaningful reading on the filament pins if all tubes are in their sockets and the power switch is turned on. Don't apply power to the set, just have the switch on. That completes the circuit to the hot chassis.

Chris K
03-21-2023, 06:24 AM
Great thank you! Will continue checking, put together a database of all the socket resistance readings and see if that gives me and anyone else a picture of what went wrong.

bandersen
03-21-2023, 08:51 AM
OK, but I don't think you need to go quite that far. First thing I do when I find a value that is way off what is expected, is to start examining that circuit.

Once a problem is detected, I like to track it down rather than look for other problems. They might very well all be connected. Fix that first problem and any others might well be resolved.

It was suggested you start with the 12CA5 because it is a crucial piece of the power supply.

Check the resistance readings, soon as you find one that is waaay off (ignore the filament), trace out the connections to that pin.

Chris K
03-21-2023, 10:55 AM
Thanks Bob for taking the time to hang in there with me on this! I will investigate the 12CA5.

Yamamaya42
03-21-2023, 01:24 PM
I tend to agree, it has to be related somehow, from what I can see, 260v C only goes to 2 points, and is fed via a 2.2k resistor, very easy to pull down, point 1 is the audio output, where you are seeing the odd resistance checks, fed to G1 via R45 (820K) pins 2-5, the other is the horizontal oscillator, via L22 & R62 @ V10 pin1.
Of course, another suspect would be C2c, if perhaps you see a lower resistance to ground on the power supply of R45 than on pins 2-5 side, one way or another, something has to be pulling that 260v C down, and the weirdness at the audio output is a yellow alert, you have to find the red! :P

Chris K
03-21-2023, 04:17 PM
OK I think I found the issue after checking resistances on 12CA5. It led me to check the C2 can electrolytic that I had cut out of the chassis and replaced with a terminal strip containing the 4 electrolytic sections. Embarrassingly, the 2.2k resistor was still attached to the c (triangle) tab on the old C2 can. So, I think if I run the resistor between the positive lead of the 100uf replaced C2 section B and the positive lead of the replacement 22uf C2 section c, that should restore voltage to 260v C. Waddya think?

bandersen
03-21-2023, 05:02 PM
Yes, that resistor feeds the 260 volt bus from the 280 volt bus.

Chris K
03-21-2023, 05:09 PM
Are pins 2 and 5 on the 12CA5 socket physically connected? I'm still getting 0 ohms on 2 and 500k on 5. I don't have the yoke speaker or CRT plugged in however. I can't see where that would make a difference.

Yamamaya42
03-21-2023, 06:47 PM
Are pins 2 and 5 on the 12CA5 socket physically connected? I'm still getting 0 ohms on 2 and 500k on 5. I don't have the yoke speaker or CRT plugged in however. I can't see where that would make a difference.

i can't say about the socket, you will have to look and see, but the tube inside is. 12CA5 = 6CA5

http://www.nj7p.org/Tubes/PDFs/Frank/093-GE/6CA5.pdf
Only diff is the heater.
you should not be getting 0 ohms, UNLESS you mean infinite resistance, from a pin not connected.

Chris K
03-21-2023, 09:20 PM
The 2200 ohm resistor was it. It's a little bit distorted because of the angle but it's got almost full vertical deflection and about 75% horizontal...all through a 200 watt bulb. I can't thank everyone who helped out enough for hanging in there with me! So excited!!!

bandersen
03-21-2023, 09:22 PM
Congrats! Try it without the light bulb. It's limiting the power to the set way too much.

Chris K
03-21-2023, 09:31 PM
Congrats! Try it without the light bulb. It's limiting the power to the set way too much.

Wow...full screen...static on screen and speaker...bright as all hell. Had to turn the brightness down about 30%.

Bob Andersen you are the man! Thank you so much for your advice and guidance!

kvflyer
03-22-2023, 08:31 AM
Congratulations!!!! Excellent and I will NOT insert that obnoxious dancing banana! :thmbsp:

Chris K
03-22-2023, 09:17 AM
Then I will! :banana::banana::banana::banana:

Electronic M
03-22-2023, 11:59 AM
Good work finding the issue!:banana::D

Yamamaya42
03-22-2023, 12:44 PM
Now it's time to post some screenshots of video from the general year the set was made, like The Twilight Zone or Bonanza! :P
In the same way I picked Lost in Space for my 1966 CTC-16XL! :)

Chris K
03-22-2023, 12:52 PM
Now it's time to post some screenshots of video from the general year the set was made, like The Twilight Zone or Bonanza! :P
In the same way I picked Lost in Space for my 1966 CTC-16XL! :)

Honeymooners...probably too early...The Munsters...that's the ticket!

Need to get it on the pattern generator and dial it in first. Then I need to buff and polish this fish smelling plastic safety cover. I've had some luck so far using automotive buffing compound but I bought a car headlight restoration kit like Bob suggested in one of his thousand Predicta posts over the years. We'll see how that does.

Yamamaya42
03-22-2023, 12:59 PM
Car 54, Where Are You?! :)

Chris K
03-22-2023, 03:38 PM
Good work finding the issue!:banana::D

Thanks so much Tom! I know I take you guys down some dark alleys chasing red herrings. I appreciate the help so much.

Chris K
03-22-2023, 03:42 PM
One of the reasons that was hard to run down is because the Sams shows it in the schematic but it’s not identified in the chassis photos and it does not have the alphabetical/numerical designation like R63 or R57. I don’t think it’s in the parts list either.

bandersen
03-22-2023, 04:23 PM
Later revisions did not use that resistor. The original Philco service info does show it.

Chris K
03-23-2023, 08:05 PM
OK power issues cleared up. I'm running a crosshatch pattern from the generator. Looks like the vertical is OK, I can get it to lock but I believe there are serious horizontal sync problems. I've got a NOS set of Holiday tubes on order in case this is a tube issue. Sound is good...tube is nice and bright, sharp and the contrast works great. The only problem is I have spaghetti for an image.

Couple of questions. How is this horizontal linearity magnet supposed to work? How do you do adjustments with it? It's basically a bar magnet on an L bracket that's wedged between a band around the yoke. It has the Philco hidden adjustment pots behind the brightness, vertical and horizontal controls. Should I wait until I have reliable tubes before I start playing around with these adjustment controls?

Thanks everyone

Chris

bandersen
03-23-2023, 08:22 PM
You push the magnet forward or pull it back. It either gives that side of the screen a slight assist in deflecting electrons or holds it back. That has nothing to do with your issue though. I'm thinking it might be more of an issue in the video amp. Like you have ringing in the video signal or the if alignment is off. What effect does fine tuning have? How do other patterns or live video look?

old_tv_nut
03-23-2023, 10:40 PM
What generator are you using?

Electronic M
03-23-2023, 11:13 PM
I get the feeling the horizontal lock is off in that picture and 3 of the vertical bars are getting smeared across the screen during retrace. I forget if this model had the H AFC SS diodes, but those are often the problem when you have good vertical sync, but no horizontal sync.

Chris K
03-24-2023, 06:24 AM
You push the magnet forward or pull it back. It either gives that side of the screen a slight assist in deflecting electrons or holds it back. That has nothing to do with your issue though. I'm thinking it might be more of an issue in the video amp. Like you have ringing in the video signal or the if alignment is off. What effect does fine tuning have? How do other patterns or live video look?

Fine tuning doesnt make it any better or worse...It doesn't help with clearing it up if that's what you mean. I haven't tried live video yet. The single cross pattern has a horizontal line across the middle of the screen and 3, equally spaced vertical lines. Single dot has 3 dots across the center of the screen left to right. Generator is a Sencore VG48. I'll try some live video in a bit.

Chris K
03-24-2023, 10:52 AM
This is a generated single cross that's supposed to be centered

Yamamaya42
03-24-2023, 11:11 AM
That screen is indicative of the horizontal oscillator being WAY off frequency, L22 tweaked way too far, or something wrong in that area? For some reason it's not at 15.734 kHz -15.625 kHz where it should be.

Electronic M
03-24-2023, 11:35 AM
IIRC these sets have a coarse horizontal frequency pot hidden inside the hollow horizontal hold pot shaft. Just need a small flat edge screwdriver long enough to reach it.

Chris K
03-24-2023, 02:39 PM
It looks like L22 was off by quite a bit. I have a picture now albeit a poor one. It's a YouTube recording of an old CNN video that in itself, isn't great quality but the picture fed out of my RF modulator is a bit snowy and not sharp. The modulator works fine as a source on other TVs. Is this an IF section issue?...maybe weak tubes?? All original tubes in it because they all tested good.

Chris K
03-24-2023, 02:41 PM
And I have no idea why photos that I'm posting the same way as I did when they were in the correct orientation are now posting 90 degrees counterclockwise.

kvflyer
03-25-2023, 07:53 AM
And I have no idea why photos that I'm posting the same way as I did when they were in the correct orientation are now posting 90 degrees counterclockwise.

Cell phone picture? It happens all of the time. You can use something like MS Paint or Adobe Photoshop to rotate the picture, save it and then post it. The orientation is embedded in the picture.

Chris K
03-25-2023, 11:24 AM
Stinky Work

Chris K
03-25-2023, 01:18 PM
Final Stretch

Chris K
03-25-2023, 02:06 PM
As good as it's gonna get

init4fun
03-25-2023, 03:40 PM
As good as it's gonna get

Very good work Chris, that looks awesome :thmbsp:

Chris K
03-25-2023, 04:19 PM
Very good work Chris, that looks awesome :thmbsp:

Thank You!!

Chris K
03-25-2023, 06:18 PM
Hi all...the picture is mostly good now. Contrast and focus are good. I can tell it's sharp because I can read small computer print on it just fine but...the picture is snowy...almost like it's not getting enough RF signal strength. I changed the tubes in the IF section and in the tuner to NOS but no change in fact, all of the tubes in the set have been replaced with NOS. I haven't done a thing to either the tuner or the IF circuit board. Any suggestions on a strategy to run this down?

old_tv_nut
03-25-2023, 09:26 PM
Have you double checked for a broken antenna connection?

bandersen
03-25-2023, 09:49 PM
Does the local/distance switch have an effect?

Chris K
03-25-2023, 11:13 PM
Does the local/distance switch have an effect?

Antenna connection is good and there is a difference between local and distance images. Not in the shop right now but the top setting was better. Still didn’t get rid of the “showiness” but it was better.

old_coot88
03-26-2023, 06:00 PM
Is there a balun (matching) coil at the tuner's input? Those frequently got popped by a nearby lightning strike.

Chris K
03-27-2023, 05:57 AM
Hi all...thanks everyone for your invaluable assistance, expertise, troubleshooting and interest. It looks like the issue with signal strength was my RF modulator. It's the little white cased, $25 unit you can find just about anywhere. I got another modulator brand that, while cheap, has an adjustable RF signal output so I got enough signal strength to get a great picture. I needed to adjust the first and second sound IF coils to dial in good sound quality and eliminate buzz. The picture looks great. I wish I could take a decent photo of it to post but no matter what I do, there's banding and strobing. On to a cosmetic cleanup of the case. The brass, of course, is modestly corroded and pitted. It's right on the edge of "ehhhh, maybe I should just leave it...ehhhh, the rest of it looks so good, do I really want to leave it like that?". I do have some very good looking brass colored paint. I'm thinking of striping and polishing back to bare metal, adding a coat of filler/primer paint, wet sanding and top coating with the brass paint. The case is in great shape. Just a few edge wear marks I need to color in with a furniture scratch marker, coat it with some wax and it should look good. I debated what to do with the CRT enclosure. I have almost exact color matching epoxy based spray paint that would make it look showroom fresh but the same rubbing compound I used on the safety plastic did a pretty nice job of cleaning the plastic shell so I'm gonna leave it for now. I'll post some pictures when It's all done. Thanks again to all who contributed your time and wisdom!

kvflyer
03-28-2023, 09:56 AM
Kinda feels good, doesn't it? It should, well done and good on ya for hanging in there.

Chris K
03-28-2023, 11:00 AM
Oh it sure does. It’s the first time I’ve had one of these sets and the fact that the 21EAP4 is blazing hot got me even more excited! I had full confidence you and Bob and all the others who contributed would help see me through. Tonight, after I fabricate the replacement for the fusable resistor, I’ll put the chassis back in and it’ll go in the showroom and get turned on once a week or so. You are so right! Feels really good!