1964 Zenith 5111 comes to life!

[Tubejunke]

Originally Posted by old_coot88

Can you post a schematic of the color section? I'm betting that the problem is something other than the crystal, based on your statement that the color was strong and in sync prior to the sudden drop-out.
Bill(oc)

I don't have a way to scan a schematic, but later today I might be able to post or send you a PDF to look at. Again, from the get go the color took maybe five minutes to come in, but when it came in it was fine. I thought for sure that it was just a weak tube that was taking longer than others to achieve enough emission to do its job. Each time I powered the set it seemed to take longer and longer, till no color at all. I have a lot of studying to do for electronics tests this coming week, but I hope to at least have time to give the color killer potentiometer a good cleaning in the next day or two. I doubt that is the actual problem, but I know that it needs cleaning as it was a bit jumpy when I tweaked it the other night. Also, I need to give the underside of the chassis a better visual inspection and maybe check out some resistors. I already found the horizontal "efficiency" coil that seems to have a broken backbone (plastic), but it doesn't seem to be causing any problems. However, it might be why the horizontal hold control is off center. For now I want to focus only on color issues.

[old_coot88]

Originally Posted by Tubejunke

...Again, from the get go the color took maybe five minutes to come in, but when it came in it was fine.

Uh-oh, my bad. I missed that statement, but found it upon re-reading the thread.
Sure sounds like like the 3.58 oscillator tube was slow warming up and finally not starting at all. Do you have a known good sub for it?

..I thought for sure that it was just a weak tube that was taking longer than others to achieve enough emission to do its job. Each time I powered the set it seemed to take longer and longer, till no color at all.

Here's assuming the problem is a weak 3.58 oscillator; with the color killer full 'on', you'd see barberpoling gradually straightening up until the color finally locks in.
(An analogous situation would occur with a weak horiz. oscillator. A good working test for the H. oscillator is to turn the set off for ten seconds or so, and then back on. If it takes a while to lock back in, the tube is borderline weak even though it may show good on a tester.)

Speaking of horiz. stuff, the 'efficiency' coil does not affect horiz. sync. But if mistuned, will cause high HOT current. It needs to be tuned for the 'dip' of minimum current.
Bill(oc)

[Tubejunke]

Originally Posted by old_coot88

Sure sounds like like the 3.58 oscillator tube was slow warming up and finally not starting at all. Do you have a known good sub for it?

By mentioning the 3.58 oscillator tube, do you mean the "Chroma Reference Oscillator? That is the only color related tube that I see that is called an oscillator. The rest seem to be amplifiers and demodulators. I will have to look for a sub, but I don't have a "known good". I will get back to the issue with the horizontal efficiency coil with what seems to be a broken backbone or housing. In short, I would think that it should be rigid, but I can grab the coiled end and it wobbles around separating the windings a bit.

[old_coot88]

Originally Posted by Tubejunke

By mentioning the 3.58 oscillator tube, do you mean the "Chroma Reference Oscillator?

Yes. What is the tube type (designation)? Since you don't have a known-good sub, how good is the emission on each section of the tube? Try dropping the heater voltage a notch (some testers have a feature called "life test" which does this). Does emission drop dramatically and then come back slowly when you restore full heater voltage? If so, it would suggest the tube may be borderline in oscillator service. Is each section free of shorts and/or gas?

...I will get back to the issue with the horizontal efficiency coil with what seems to be a broken backbone or housing. In short, I would think that it should be rigid, but I can grab the coiled end and it wobbles around separating the windings a bit.

Yes, that coil form should be rigid and not wobbly at all. It crystalizes from heat and gets crumbly over time. Are you monitoring the HOT cathode current? It may be high since the coil is no doubt detuned from the 'dip' it was originally set to.
In Zeniths, the plastic coil forms on the convergence panel are also prone to crumbling and getting wobbly.
Bill(oc)

[Tubejunke]

Originally Posted by old_coot88

Yes, that coil form should be rigid and not wobbly at all. It crystalizes from heat and gets crumbly over time. Are you monitoring the HOT cathode current? It may be high since the coil is no doubt detuned from the 'dip' it was originally set to.

No, I have not checked that. Another person has posted saying that his set had similar problems and that the coil should be replaced. Would I use an amp clamp or break a connection and connect an ammeter in series to check this current?

[compucat]

Originally Posted by Tubejunke

By mentioning the 3.58 oscillator tube, do you mean the "Chroma Reference Oscillator? That is the only color related tube that I see that is called an oscillator. The rest seem to be amplifiers and demodulators. I will have to look for a sub, but I don't have a "known good". I will get back to the issue with the horizontal efficiency coil with what seems to be a broken backbone or housing. In short, I would think that it should be rigid, but I can grab the coiled end and it wobbles around separating the windings a bit.

When I first got my Zenith roundie the horizontal output tube was glowing red at the plate. The problem was a damaged horizontal efficiency coil. The coil form was broken and the windings were loose on it. After replacing the coil the problem went away. It would be wise to replace that coil before it fails otherwise you risk damaging the horizontal output tube and/or the flyback.

[Tubejunke]

Originally Posted by compucat

When I first got my Zenith roundie the horizontal output tube was glowing red at the plate. The problem was a damaged horizontal efficiency coil. The coil form was broken and the windings were loose on it. After replacing the coil the problem went away. It would be wise to replace that coil before it fails otherwise you risk damaging the horizontal output tube and/or the flyback.

This is exactly what mine did at first (but with smoke), but replacing the tubes I mentioned in another post brought the HV to life and the red plate, smoke etc. went away and became a nice, well aligned picture. Now I don't even want to turn the set on!

Where in the world can I find an original replacement for THIS, or is it unobtanium?