Rca or zenith

[bgadow]

Chevy vs Ford, Coke vs Pepsi. Open to much debate. The Zeniths I've seen seemed to be better built but, from that era, I'd say RCA had a slight advantage in pictures. A tough call because individual sets tend to have big differences, especially at 50+ years out.

[old_coot88]

Regarding a Zenith roundie, the very first thing I would determine is whether its 'efficiency' coil is wound on a brown phenolic form (good) or the later whitish, semi-translucent plastic form (bad). If the latter, I would absolutely pass on the Zenith. The form crystalizes and falls apart from heat and age, This detunes the coil, causing the H.output tube current to skyrocket, rendering the TV set unusable. And those coils are near-unobtanium.
(The blue coils on the convergence panel usually suffer the same crystalization problem.) Earlier Zeniths used phenolic forms here as well as in the eff. coil (good).

[Tubejunke]

Originally Posted by old_coot88

the very first thing I would determine is whether its 'efficiency' coil is wound on a brown phenolic form (good) or the later whitish, semi-translucent plastic form (bad). If the latter, I would absolutely pass on the Zenith. .

This problem was the first of a line of heartbreaking events that came along with my bringing home a Zenith 5111. Looking back now, nothing was any real catastrophic failure. I believe that the crusty (brown) form did cause several other issues which had to be addressed due to the high current in the horizontal output circuit.

The big problem was that at the time there were two possibles of retailers with replacement coils known to exist; one being Moyer Electronics and I can't recollect the other which is who I ended up getting mine from for ten bucks more than Moyer wanted. When I began posting about this problem Moyer had three in stock. I waited about a week to order and someone had bought ALL of them. They told me they hadn't sold one in years till that week! Luckily they were nice enough to give me the name of this other place who had one and I had to jump through hoops to get them to send it to my house. Turns out that they had quit sending out small orders to jobbers like TV repairmen years ago and had evolved into some larger business model, but they still had the inventory and were nice enough to accommodate me.

Now what they sent was an N.O.S. Thordarson replacement and it was the "whitish, semi translucent" part that OldCoot said are bad. Being new like it is, I don't have a fear in the world of it breaking apart on me. Will it last as long as the original didn't? Who knows, but I am happy beyond happy to have what seems now to be nonexistent on the market. The true sad part is that there must be tons of these chassis sitting around in people's hoards and I couldn't get anyone to yank me one and bail me out of what was a big mess. The VK community really never works that way at all. Many nice folks have helped me here and I have done the same in return. One or two did look and theirs were no good. These chassis were around the better part of 10 years! Somebody has a bunch. Maybe not here, or looking at that time.

Even so, RCA or Zenith? I still would say Zenith. Everyone seems to have an RCA because they are talking about repairing them. Less is mentioned about Zenith because quite often they are in the corner playing. No crappy PC boards to deal with and MUCH better flybacks with Zenith. So I wouldn't let one little coil stop me from owning one. We VKers need to put this coil thing to a think tank and come up with a solution! It can't be that hard...

[zeno]

Better picture is a matter of taste mostly.
Better built Zenith for sure. No dried up PCB's to deal
with. Hoz eff coil can be dealt with, its mostly a matter
of fit.

73 Zeno

[iong]

Thanks for all the replies. I only have room for two roundies and one I'm keeping is the ctc-5 table top. I was afraid the 29jc20 first Zenith color would not have as nice a picture as other Zenith roundies but if it's hard to tell I would like to keep this one. It's also SC400 (tuner motor gets power but doesn't work) It's the Cambridge 6035. I wondered about flyback life because the high voltage cage has no ventilation. All the later chassis do.
Perry

[Jon A.]

Originally Posted by zeno

Hoz eff coil can be dealt with, its mostly a matter
of fit.

73 Zeno

I'd like to know how to do that. I never know when it might be needed.

I also need to look up the selenium stinkpot replacement info and write it down.

[zeno]

Originally Posted by Jon A.

I'd like to know how to do that. I never know when it might be needed.

I also need to look up the selenium stinkpot replacement info and write it down.

Electronic M covered seleniums well so.

If you cant find NOS eff coil IIRC they were wound on the same
form as convergence coils but its been 30 yrs !!. You can rewind
on an old form & change the slug. Using a sub requires mounting
change, not my strong point..... You can also add or remove
windings to get the wrong value in range.

73 Zeno

[Jon A.]

Originally Posted by zeno

Electronic M covered seleniums well so.

If you cant find NOS eff coil IIRC they were wound on the same
form as convergence coils but its been 30 yrs !!. You can rewind
on an old form & change the slug. Using a sub requires mounting
change, not my strong point..... You can also add or remove
windings to get the wrong value in range.

73 Zeno

Thanks. That's where redneck engineering comes in for me. Working on a minor fit problem now. I should be able to get the Tatachi running like new.

[Electronic M]

Originally Posted by Tubejunke

We VKers need to put this coil thing to a think tank and come up with a solution! It can't be that hard...

Those efficiency coils and a number of other Zenith coils used the same plastic form....The best solution would be to get an intact original plastic form get it 3D scanned and 3D print a few dozen (or do a mold and cast process). With new forms most old coils could be rewound by hand with reasonable patience.

[Zenith6S321]

I have a 1955 RCA 21CT55 and a 1963 Zenith 29JC20 restored and both produce good color pictures. Here are links to the restoration threads with pictures of the results:

RCA 21CT55
http://videokarma.org/showthread.php...=21ct55&page=5

Zenith 29JC20
http://videokarma.org/showthread.php...=29jc20&page=7

The RCA 21CT55 has wideband color demodulation so you can see finer detail in the color. Its early CRT has dimmer phosphors but really nice colors. The fine tuning has to be adjusted carefully to minimize color and sound IF interference visible in the picture.

The Zenith has the 21FJP22A with rare earth phosphors that are brighter and good color, but I prefer the 21CT55 color. The Zenith has the narrow band demodulation so its has a softer color picture than the RCA. The fine tuning is much more forgiving than the 21CT55.

I like both of them very much. I tend to watch the Zenith more, mainly because I feel it does not push its components (such as the flyback) as hard as the RCA. I have installed low speed cooling fans on both sets flybacks, just in case. The Zenith flyback runs cooler than the RCA.

Dave