1970s Zenith Console - Troubleshooting - Page 2 - Videokarma.org TV - Video

ThePlague · #16 04-07-2022, 05:43 PM

Hello all,

Thank you for all of the advice and tips! I have 3 of the 5 22-5001s in. Once I have all 5 and install them I will begin troubleshooting based on your recommendations!

This is going to be a big project, but will be more than worth it in the end.

zeno · #17 04-08-2022, 06:59 PM

The main thing is getting the HV up now & a raster. That way
you can be sure the CRT is strong before spending too much $$
on it.
Sounds like the tripler may be bad. Unhook the wire from the flyback
donut to tripler. At the flyback end you should get a nice 3/8 arc
into the air if you put a screwdriver near it. Will also stop tripping
the breaker.

Zeno

ThePlague · #18 02-04-2023, 03:59 PM

Hello all! I apologize for the delay. Got a new job, moved across the country, and now finally have some spare time to put into troubleshooting.

I got the base off and found these items upon inspection. It looks like one the safety capacitors (white) got quite hot at one point.

Also there this blue ferrite disc (choke or inductor?) that is broken in half. I need to get ahold of the schematic to figure out what it is and for.

I am currently working on previously mentioned troubleshooting steps.

ThePlague · #19 02-04-2023, 04:37 PM

Upon lifting the leg of the motor capacitor, I still have the same symptom of audio buzz and then the breaker blowing after a few seconds. There is no filament glow in the tube neck.

Update 1: Upon inspection of the chassis circuit diagram, the blue disc is R324 22 ohm thermistor for the degauss coil.

Update 2: After seeing the 22-5001 scorched on the chassis, I replaced all 3 on the unit with Zenith replacements. Looking at the HV tripler, is this the original unit or is this a replacement unit that combined the focus divider? It is a SCI 7234 "212-139".

Update 3 (closer to the issue): I checked out Q801, 802, 803, and 804 on the Horizontal Output module and they checked out good and within specifications. I replaced the HO module and removed the screws to the Horizontal Output Transistor and the breaker did not blow. The Filament in the neck is glowing. Seems like its either this transistor or the tripler. Will pull the transistor and check it out.

ThePlague · #20 02-04-2023, 09:06 PM

Update 4: I pulled the Horizontal Output transistor Q216 and measured collector to base and collector to emitter for a short. I did not find any.

I reinstalled Q216 and unsoldered the input from the flyback to the tripler. It is still tripping the breaker and there is no high voltage crackle.

According the schematic after Q216 there are multiple capacitor that could have failed and are shorting to ground. I will begin checking these.

zeno · #21 02-05-2023, 09:20 AM

Check the damper 103-193 IIRC subs 103-287
That red blob looks like it was the focus diivider got to deal
with that.
If it works with HOT screws out that usually means bad HOT or tripler.
BUT there are huge spikes on the HOT C. May be one of the caps
breaking down but not showing a DC short.

Zeno

ThePlague · #22 02-06-2023, 01:01 PM

Hey Reno,

I'll take a look at that this evening. To be honest, if I can find a tripler that has an internal focus divider I wouldn't mind swapping it out rather than dealing with that orange blob. I remember a forum post listing suitable replacements if I can dig that up.

I hope that something truly failed given the original power on event of a sulfur burning smell; that would make diagnosis much easier.

BeamT · #23 02-06-2023, 08:30 PM

+1 on Zeno's last reply. In addition to the damper I would also investigate C261 which is just off the collector of the HOT. I'm looking at Sams 1312 and that cap may actually be a "feed thru" It will have a pin on each side of a flange, the flange is grounded, usually soldered to the chassis or a metal bracket. Sams lists this cap as 22-5395 .001 @ 1.2kv

If you are interested, google for a YouTube:
"Troubleshooting the 1973 Zenith 25DC56 Color Television Chassis" by drh4683.
Very good video, methodically troubleshooting the same chassis and circuits you are working with. Breaker popping, he locates a shorted safety cap. There may be a view of C261 in the video. He is also troubleshooting with the Zenith CM manual.

I am working on a 25DC56 and posting in the Solid State sub-forum. I haven't attempted to power my set up yet. I'm waiting on the safety cap subs from Mouser. If any of mine are open, I wouldn't be running it that way for any length of time, and if any of mine are shorted, not going anywhere anyway. So replacing them first is a good initial step, troubleshoot the rest after that.

My tripler, 212-139 is original as is my 63-9012-2 focus divider.

The red blob is your focus divider covered in HV-putty, was a replacement that started to arc. Sams lists 63-9896 as a replacement. I'm not sure about that....

BeamT · #24 02-06-2023, 08:49 PM

BTW I'm away from my set or I would have checked for C261 and sent a picture.... If it is a "feed thru" it doesn't look like a typical capacitor.

ThePlague · #25 02-06-2023, 10:51 PM

Hey Todd,

That was my first suspect cap. I have actually watched the video you mentioned and picked up a few tips from that. I am also using a Sams and its proven quite handy when identifying chassis components.

C261 is a weird little thing. It is however the last component before my safety cap that got nice and toasty. I'll have to take it out of the circuit and test it.

Should you have any issues getting your safety cap replacements, I have a Zenith 22-5001 OEM replacement and a Associates equivalent left over. (I thought there were 5 safety caps, but I have only seen 3 so far)

I greatly appreciate the help!

BeamT · #26 02-06-2023, 11:05 PM

It is a feed thru, its located in the bracket that is immediately to the side of the HOT socket. one end is connected to the yellow wire. It looks like a resister with a collar around it.

Not sure how you feel about your past steps but this might be a good time to regroup and repeat and verify some of your work. Zeno's advice is quite sound.

Can you post a picture of the 3 safety caps you replaced?

Have you checked the damper diode?

You can check the feed thru cap with an ohmmeter but that does not rule it out as a problem. It may not be shorted with a DC voltage present but if you put the screws back into the HOT, the horiz circuit will start and the AC voltage there is quite high. From the HOT socket, collector pin, what sort of resistance to ground are you seeing?

BeamT · #27 02-06-2023, 11:09 PM

NVM, you are correct. I needed to look closer. There are 2, one on the base, the other, you have circled, is the collector.

zeno · #28 02-07-2023, 07:57 AM

Usually 2 caps are on the flyback & 3 more under the chassis.
If any got changed to orange ones you may miss them.
Feed thrus are known to go but its rare. I think I had 2 or 3
all on the 13GC10 13" chassis.
I did see a NOS triple at one of the distributors BTW. Try to stay original.
BTW I hope that putty was put on by the owner. If it were a tech
I would fire him. Lucky they didnt see fire trucks !!

Zeno

ThePlague · #29 02-07-2023, 04:49 PM

Quote:

Originally Posted by BeamT

It is a feed thru, its located in the bracket that is immediately to the side of the HOT socket. one end is connected to the yellow wire. It looks like a resister with a collar around it.

Not sure how you feel about your past steps but this might be a good time to regroup and repeat and verify some of your work. Zeno's advice is quite sound.

Can you post a picture of the 3 safety caps you replaced?

Have you checked the damper diode?

You can check the feed thru cap with an ohmmeter but that does not rule it out as a problem. It may not be shorted with a DC voltage present but if you put the screws back into the HOT, the horiz circuit will start and the AC voltage there is quite high. From the HOT socket, collector pin, what sort of resistance to ground are you seeing?

I will check this this evening and go back through and verify.

Quote:

Originally Posted by zeno

Usually 2 caps are on the flyback & 3 more under the chassis.
If any got changed to orange ones you may miss them.
Feed thrus are known to go but its rare. I think I had 2 or 3
all on the 13GC10 13" chassis.
I did see a NOS triple at one of the distributors BTW. Try to stay original.
BTW I hope that putty was put on by the owner. If it were a tech
I would fire him. Lucky they didnt see fire trucks !!

Zeno

I didn't see any other orange ones that looked like my replacements. Looking through the SAMs I only see C268, C267, and C265 listed as 22-5001 capacitors. I replaced the 2 on the flyback and the one right after the HOT. Do you happen to know the designations of the other 2?

I was looking online and had no luck finding a 212-139 tripler for sale. Fingers crossed this one is okay. However, that focus divider is a mess. I do plan on replacing that at least if the tripler turns out okay. This was a one owner set and based on its heavy usage I doubt it was done by the owner.

ThePlague · #30 02-07-2023, 10:18 PM

I went to check HOT collector to ground and sure enough there was continuity. There was also continuity between the HOT collector and emitter. I took the HOT out and rechecked the circuit without it. The collector side of the circuit was no longer grounded.

Long story short my HOT has failed and I was checking continuity for the collector (threads) incorrectly. There is a short from collector to emitter and collector to base. I will be sourcing a replacement.

I have also attached the requested pictures of my 22-5001 caps. They are in for troubleshooting rather than looks at the moment.

Update 1: From a quick glance, the Zenith replacements are all but gone. I was able to find sources for the RCA SK3115, Sylvania ECG165, and NTE165 replacements. Of course OEM is preferred, but is there any pecking order on other brand replacements?