View Full Version : 68 Zenith 25" color console


Adam
07-08-2016, 02:59 PM
20Y1C48 chassis

Basically works. I see an occasional light or dark horizontal line flash across the screen, I've seen this before caused by a corroding connections in the CRT socket. And it has the green halo, not that noticeable with the set on. The tube was replaced in 71 and is good otherwise.

This is going to be my new front room set. It isn't an exact matching pair, but it looks like it belongs with the '66 Zenith console stereo I also have sitting out here. The TV I was using out here before is a '77 CCII console with a good chromacolor 23V tube, I'm thinking I'm might just swap the tube and socket from the '77 into the '68.

DaveWM
07-08-2016, 06:30 PM
move the video out tube around and see if you can effect that problem. IIRC there was a note in the zenth service manual about cold solder joints to the video out.

zeno
07-09-2016, 10:06 AM
The ends of the terminal strips would crack open & go
very int. Seemed most common on tin cans. Sometimes there
are also grounds along the strips & at the tube sockets.
Poke them with a screw driver & see if they move.

73 Zeno:smoke:

Adam
07-11-2016, 07:41 PM
Whatever was causing that, it somehow managed to fix itself:banana:

Except for the green halo the picture looks great, and the convergence and purity is spot on. I still think I want to eventually swap in that chromacolor tube out of that CCII 23V console, but I don't think I'll do it for a while.

Olorin67
07-11-2016, 10:12 PM
If you do swap tubes, I'd be interested in the old one. I have a 66 or '67 Zenith metal tabletop with a rather weak CRT.

Adam
07-13-2016, 12:25 PM
The hard part would be getting it to you. Is anyone is planning a TV run between MI and WI this summer?

Electronic M
07-13-2016, 02:19 PM
If someone does I have a set that needs to get to it's buyer in MI....

Adam
07-15-2016, 04:04 PM
I'm going to try this tube swap. The new tube is a 23VCMP22. Does anybody need any parts off of that 25JC49 chassis? Or want the cabinet? Otherwise my plan is to keep the chassis for parts and dump the cabinet.

Electronic M
07-15-2016, 07:21 PM
Why not do a full CRT swap and keep both sets usable?....And while your at it you might want to unplug your cat or have it exorcised. :D

Adam
07-15-2016, 08:03 PM
I bought 6 consoles in the past 3 months. I'm up to a total of 14 consoles! And that one is a little water damaged on the top, and it's a cabinet style I don't like much anyway.

Adam
07-15-2016, 11:25 PM
Well now I know the 23VCMP22 for 25GP22 swap works! That problem I was having before came back, but I found out it was just being caused by a dirty IF tube socket.

Adam
07-16-2016, 12:18 PM
So everything was working great, but I hadn't put that metal enclosure around the back of the CRT. (What is the point of those things anyway, except to hold the auto degauss coil and make it really hard to put in a CRT?)

And the new tube was a little wider than the original because it has one of those metal bands around it, where the original didn't. I wound up removing two of those little pieces of cushion material on the corners of the surround/mask on one side to get the tube in, but after that everything fit great.

But when I went to try to side that metal enclosure in there was no room for it to slide between the CRT and the surround/mask it fits into on that one side. After messing around with it for several hours with no luck, I finally just cut off most of the front edge of that enclosure on one side (just the first 1" or so where it slides to the side of the CRT on that one side), and that got it to fit.

By that time it was pretty late and I was tired. I wasn't looking at a clock but it had to be between 4:30-5AM because the Night Gallery was on. So I was really tired and I got it all back together, but forgot to connect up the HV. I turned the set on, and that HV lead sitting on the chassis arcs to something … and whatever it took out is keeping me from getting H or V sync. :sigh: (From what it looks like the oscillators are fine, but the sync pluses aren't getting to either the H or the V osc)

Then I got out a schematic, sat down on the couch to look at it, and fell asleep...

Adam
07-16-2016, 03:42 PM
I must have really been out of it late last night. All that sync trouble was just a tube that got pulled out of the socket a little.

Remaining problems are that convergence needs to be redone, and those horizontal lines are back. It seems to be responding to shaking the tuner. I lubricated the gears in the tuner last night so now it's actually possible to change the channel (before the uhf was frozen stuck). I'll take the tuner back out and clean the contacts inside.

Sometimes you really shouldn't work on stuff after you get tired. Last night I knocked into a picture on the wall which fell and put a dent in the top of the otherwise nearly perfect cabinet of my 66 Zenith console stereo (I was holding a CRT at the time so I couldn't grab the picture as it was sliding down. And in the process of doing that I pulled out the power cord on this video modulator/switch I use and now I have to resolder the socket it plugs into.:thumbsdn:

consoleguy67
07-16-2016, 06:42 PM
Get some sleep.

Adam
07-16-2016, 07:14 PM
It works, no more green halo, no more mysterious horiz lines, good convergence…the channel # light just burned out, but that's easy to change… I'm going to bed early tonight:banana:

Crappy cell phone pics, my digital camera just quit (says it's the memory card, but I don't have another one to test).

Electronic M
07-16-2016, 07:36 PM
Try licking the contacts on the card and puting it back in the camera (the old A Christmas Story dark Christmas light trick)....Mine needs that occasionally.

Telecolor 3007
07-16-2016, 07:55 PM
How did you manage to put "Netflix" on that tv? An andorid receiver?

Adam
07-16-2016, 08:24 PM
Something called a Roku with a composite video output connected to an RF modulator.

Well, almost immediately after I posted that the color went out. But a new (used) 6GH8 and adjustment of the color oscillator seems to have fixed it.

I'm all out of new 6GH8s (I still have several good-used), I don't know what we're going to do if the supply of those ever run out, they're the one tube in old color TVs that seems to go bad frequently…

Now just to change that channel light, and I can put this back together and watch Star Trek on this set at 9. Despite the fact that I can watch any episode I want whenever I want on Netflix, and I have about 2/3 of them on DVD and a few on VHS, I still really enjoy watching it on over-the-air tv every Saturday at 9PM. 30 years ago in the summer of '86 I had just gotten my first tv (an early 70's Zenith 16" B&W with a tube chassis in a plastic cabinet) and I used to watch Star Trek on ch44 at 8PM every Saturday night. Now it's on ch47.2 and I have to use a converter box, and I've seen every episode many many times, but I still like doing it.

Electronic M
07-16-2016, 08:49 PM
I'm all out of new 6GH8s (I still have several good-used), I don't know what we're going to do if the supply of those ever run out, they're the one tube in old color TVs that seems to go bad frequently…
.

Grab some 6EA8s, 6U8's and other compatible types (wanna list?), and hope the supplies of those don't run out...:D

fixmeplease
07-16-2016, 09:05 PM
How did you manage to put "Netflix" on that tv? An andorid receiver?

You need a roku 1 or an old roku 2 that has the composite hookups. They only make one model that still has it new, but you can find a few used roku 2's on ebay that have it too. You might need a modulator too if your tv doesnt have the hookup.

Adam, after you sleep, can you post a pic of the whole tv from the front. Your first pic shows it at an angle and not close. Its a beauty and I'd like to see it better, including the cabinet. Thanks!

Adam
07-16-2016, 10:15 PM
Here it is (The color didn't go out again, that's a b/w program!)

fixmeplease
07-17-2016, 09:28 AM
Thanks Adam! Very nice looking set.

Adam
07-22-2016, 04:47 PM
The problem with the black horizontal lines came back worse. The problem with problems like that is that there are so many things that could cause it, that you think might be causing it, that aren't actually what's causing it. It got worse if I turned the brightness up. If the brightness way all the way up it would do it continually, so I turned it all the way up, put a mirror in front of the set and went behind it to see if I could poke around and find the cause. I could hear something in the HV cage, and the problem turned out to be a dirty 3A3 socket.

I swapped the 3A3 first, even though the tube in there was a new 3A3C (the original one was bad), and the problem improved but didn't completely go away. Then I sprayed some contact cleaner in the socket and pulled the tube in and out a few times and that seems to have fixed it completely. Then I put the first new tube back in and made sure the problem was just the socket and not the tube. But I had also found a new one of those solid state 3A3's in with my tubes and I thought I would try it, and that's what I left in there. The HV went up with the ss one, but I adjusted it back down. Are those ss 3A3's any better, or should I put the regular tube back in?

Electronic M
07-22-2016, 05:32 PM
The SS are more reliable , don't load the fly as heavily, and tend to produce more HV...All good things.

zeno
07-22-2016, 05:35 PM
SS HV rectifiers were no better than tubes. Big advantage was if
the filament winding was arcing you could cut it out. On some
sets its a real PIA to change.
Pull the socket & check for rot. Also pull the cup clean & check for
pin holes. Also pull the bottom cover from the cage & look
for arcing around the focus area.

BTW that was our 1st color set but ours was maple. Still ran good
in the mid 80's when we gave it away. Only a few tubes
& the rectifiers were changed. VERY reliable for an all tube set !
Jug was still fine also.

73 Zeno:smoke:

Adam
07-23-2016, 04:37 PM
This turned into one of the strangest TV repair problems I've seen:

So I sat down to watch TV and eat dinner and after a few minutes it lost HV entirely. That ss 3A3 just went out. So I put a tube 3A3 back in… and my black horizontal lines were back.

Then I remembered that a similar effect was caused by the HV rectifier filament winding arcing to the chassis on a CTC-10 I had. So I change that (which isn't nearly as easy to get to in this set as it was in the CTC10). But that didn't fix anything.

Next, even though I had looked at the cup and cleaned in there and it looked ok to me, I decided to try another. I had a used spare cup and socket I knew was good that I had pulled from a '68 Zenith 21" color metal cabinet set I had parted out about 10 years ago, and it was identical to the ones in this set. The problem was still there after I swapped in those, but it sounded like the arcing I was hearing that I was previously sure was in the HV cage before was coming from somewhere else...

If you look at the pic, you can see that spring going across the back of the CRT. It was that that was arcing (to itself and to the CRT), and I removed the spring and the problem went away, completely. But, if I cranked the brightness all the way up it would occasionally arc from one of the yoke-holding springs to the CRT, so I moved it to the other side of the yoke (where there was no label) and it seems ok now. It seems as if the problem was caused by that spring being over that label. Initially the label was insulating the spring from the CRT and it was like not having the spring there at all (and the problem went away). Then it burnt a few holes through the label (which you can see in the picture) and then the arcing started and the problem resumed.

But that doesn't explain what caused that solid state 3A3 to go bad so quickly. It also doesn't explain why it was doing it with the other CRT in there (but not nearly as badly) with no label in that place. Could that cup have been starting to break down but mostly ok, and that was contributing to the problem as well?

Also there was a small resistor (10 ohms 2W) in series with the 2nd anode, placed under the 3A3 socket on my set. But it was nowhere to be found in my schematics for the 20Y1C48 and there wasn't one connected to the other socket I swapped in either, so I just left it out. It doesn't seem to make any difference, but should I put one back in, or is it ok to just leave it out?

Electronic M
07-23-2016, 04:55 PM
This turned into one of the strangest TV repair problems I've seen:

So I sat down to watch TV and eat dinner and after a few minutes it lost HV entirely. That ss 3A3 just went out. So I put a tube 3A3 back in… and my black horizontal lines were back.

Then I remembered that a similar effect was caused by the HV rectifier filament winding arcing to the chassis on a CTC-10 I had. So I change that (which isn't nearly as easy to get to in this set as it was in the CTC10). But that didn't fix anything.

Next, even though I had looked at the cup and cleaned in there and it looked ok to me, I decided to try another. I had a spare cup and socket I knew was good that I had pulled from a '68 Zenith 21" color metal cabinet set I had parted out about 10 years ago. The problem was still there after I swapped in those, but it sounded like the arcing I was hearing sure was in the HV cage before was coming from somewhere else.

If you look at the pic, you can see that spring going across the back of the CRT. It was that that was arcing (to itself and to the CRT), and I removed the spring and the problem went away, completely. But, if I cranked the brightness all the way up it would occasionally arc from one of the yoke-holding springs to the CRT, so I moved it to the other side of the yoke (where there was no label) and it seems ok now. It seems as if the problem was caused by that spring being over that label. Initially the label was insulating the spring from the CRT and it was like not having the spring there at all (then the problem went away). Then it burnt a few holes through the label (which you can see in the picture) and then the arcing started and the problem resumed.

But that doesn't explain what caused that ss 3A3 to go bad so quickly. It also doesn't explain why it was doing it with the other CRT in there (but not nearly as badly) with no label in that place. Could that cup have been starting to break down but mostly ok, and that was contributing to the problem as well?

Also there was a small resistor (10 ohms 2W) in series with the 2nd anode, placed under the 3A3 socket on my set. But it was nowhere to be found in my schematics for the 20Y1C48 and there wasn't one connected to the other socket I swapped in either, so I just left it out. It doesn't seem to make any difference, but should I put one back in, or is it ok to just leave it out?
Dude! Those springs are supposed to be in contact with the aquadag on the outside of the CRT, and should have some electrical connection to the chassis. If the springs don't contact the dag then the HV becomes unfiltered (a bad thing)!

The inside of the CRT is coated in aqua dag connected to the HV button, the out side of the dag is connected to ground. the 2 separate dags separated by glass form a HV capacitor of roughly 5000-50000pF depending on bulb size, etc. (IIRC). You need to fix the arcing issue. The spring SHOULD contact the outer dag, and do so firmly without arcing. If un-grounded it will stress the HV rect, and flyback, and if arcing to ground there is risk of CRT implosion as those arcs can locally super-heat the glass*.

*Ever seen those youtube videos of people imploding 90's CRTs (which had better implosion protection) by setting plumbing soldering torch flame on the face of the CRT?...Arcing does the same thing.

Adam
07-23-2016, 05:13 PM
Well it's not a problem anymore, I moved the spring to the other side of the yoke where it's up against the CRT with nothing in-between.

But this doesn't make sense to me because everything is already grounded even without that spring. There's a grounding strap connecting one of the corners of the frame that goes around the CRT to the chassis. The copper ring which tightens around the CRT to hold it in place (and is in direct contact with the coating) hooks to that grounded frame and so do the 4 springs which hold the yoke in place... I checked just now with the ohm-meter to be sure - all that stuff is grounded.