68 Zenith 25" color console

[Electronic M]

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]

How did you manage to put "Netflix" on that tv? An andorid receiver?

[Adam]

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]

Originally Posted by Adam

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...

[fixmeplease]

Originally Posted by Telecolor 3007

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]

Here it is (The color didn't go out again, that's a b/w program!)

[fixmeplease]

Thanks Adam! Very nice looking set.

[Adam]

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]

The SS are more reliable , don't load the fly as heavily, and tend to produce more HV...All good things.

[zeno]

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

[Adam]

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]

Originally Posted by Adam

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]

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.