Two new Zeniths

[Charlie]

Originally posted by Steve D.

And Charlie, I know this started out as a progress report on your two Zeniths. I guess it got hijacked along the way, but you've done a great job wedging your posts into YOUR thread.

Steve

And i thought everyone forgot all about me!

Well, as far as the roundie set, I went today to the parts house. They didn't have the 80/475 caps, but have ordered them for me. I got the 4/450's, and installed them, but only made some small differences. The B+ is about 50 to 60 volts too low, so I am hoping those three 80 mfd caps will correct it.

I was looking closer into the HV cage, and noticed that the flyback transformer in this thing is built like a rock! No chance of dripping wax like an RCA!

My only other wonder in the HO tube. Yeah... ya'll remember? Supposed to have the 8 pin 6DQ5, but has a 9-pin socket? So far, it APPEARS to be a factory installation of the socket. Maybe I should try looking to see if Sams listed in production changes in the index.

[Charlie]

just learned earlier that there was a production change bulletin for this chassis listed in Sams 939-3. My Sams don't go quite that high, so if anyone has it, would you look and see what the production change was related to? It sure would help if it turns out it was related to the HO tube!

Kinda funny to think that it was so long before this PCB was published... from 599 (the set the original schematic was in) all the way up to set 939... that's about 6 years.

[bgadow]

An amazing amount of stuff being covered in this thread!

TV Audio: I would much rather be listening to my 25MC33 or CTC-5 then to one of those new black box tv's, no matter that they are stereo. Who cares, with those crappy speakers?

Zenith: Seems like I've seen mexican Zenith stuff from the 70s-maybe just the modules were made there? Seems like they were sourcing radios & b/w tvs by the mid-70s from Taiwan mostly; one Zenith radio I have from that time period was made by GoldStar so I guess it was a longstanding relationship. Towards the end there really couldn't have been much left to do in an American Tv plant, just assembling the chassis (imported from Mexico or Asia) the crt (maybe still American made) and the cabinet (likely made by another company) I'd guess that it was only the cost of shipping the heavy crt's around the world that kept many companies here as long as they were. (I gather that there are still a number of companies making new crt's in the USA)

There was an interesting history of Admiral in Radio Age a year or so ago and it made light of the troubles they had making their own color picture tubes; they never did get them right, apparently. It would be interesting to get the whole story on that one. I recall that through the 80s and early 90s whenever Consumer Reports tested tv's they mentioned a greenish cast to the pictures of Zeniths. I remember comparing them in Sears or other stores and kind of wanting the Zeniths to make the best picture but they were always the worst of the bunch. The only later model set I saw in daily use belonged to the woman my wife used to board with. The color was okay but the pincushion circuit must have been totally dead.

And as for the root of this thread: maybe the "compactron" was just used in a short run, maybe an experiment or a way to use up some stock, or just used at the end of the run?

Another note: today I stopped by the local freight salvage store. Sometimes he will have some older items in there (maybe selling for a friend) and today he has a clean System 3 Space Command console w/Zoom. $99.99. There was a time when I would have bought it but have to save room for other things.

[Chad Hauris]

As far as I know Zenith never used the 6JE6 (9-pin Novar tube) as a factory design...the only non-octal H.O. tubes used on Zeniths appear to be 12-pin compactron bases.

There have been times when I converted a set that used an odd ball tube to something more common to simplify replacement (and future replacement)...this may be what happened here.

[Charlie]

After several weeks of being on the back burner, i've finally got around to installing the new capacitors into this 29JC20Q. I've got all of the lytics changed, and probably just more than half of the black beauties out of there.

Things are beginning to shape up some, but I still have a good ways to go. Convergence is way off, the verticle rolls after a while, and the screen needs to be demagnatized. Audio is still lacking just a little, although it is much better than it was and the A/C hum is finally gone.

So far i have only changed a couple of tubes, while most of them I do not have. This set uses quite a few tubes that aren't as commonly seen. I have a friend here in town that probably can cover those for me.

TV reception isn't the greatest in my garage, so that doesn't help matters much, either.

While the horizontal circuits seem to be quite stable, i still need to get in there and see what kind of current is coming off the HO tube... especially since the tube I have in there is not what the book calls for. If you recall, this set is supposed to use the 8-pin 6DQ5 HO tube, but the chassis has the 9-pin socket, and I have a 6JE6 in there right now. Like i said, it seems to be working fine, but checking those voltages and currents would probably be a good idea.

Also noticed that the HV is a little low... around 21K. Book says it's supposed to be 24K. This may or may not be related to the HO tube issue. I did swap in a new 3A3, but that made no difference in the HV.

A couple of photos below show some progress.

[Charlie]

and another...

[nasadowsk]

I've got a 25LC20 chassis - where did those sit in terms of Zenith's development of color TVs? I think it's from '63 or '64 - it uses a 21FBP22. This was right when they were going over to the metal can Xtal, as opposed to the 'tube envelope' one.

It's functional, but I still can't get the color or alignment just right But it's had ZERO capacitor replacement. I hate aligning TVs, and hate aligning colors even more. I can barely get the curves shown in the book, and that's assuming the sweep alignment rig works right. Anyone got any hints on a good sweep/marker setup? I have the RCA WR-whatever boxes, they work, but are flakey as heck, and cables EVERYWHERE.

Oh yeah - anyone else with a 25LC20 here? Mine's got 1 core in T4, but the print shows 2 cores and the book seems to suggest it too. Should I assume only 1 was a running change?

The tube is weak, too. Does anyone still rebuild these? I've heard VDC (?) does it, but every time I call....

The color killer is messed up (I suppose MOST of the the set is...) it's more like a 2nd color control than a killer.

But, it works! And that's 1/2 the battle.

I have a CTC-16 next to it, that also needs repair, and has by far the most 'nervous' horizontal hold I've ever seen - it jitters back and forth a LOT. It's also not very sensitive, despite being a Nuvistor tunner...

I have in the basement a Sylvania 580 (CTC-15 knockoff). The vertical died on it a while back and I'm too lazy to fix it now (HUGE set).

Was Zenith the only ones who used those funky beam switch tubes for the color?

To my knowledge, Zenith was the only manufacturer which used the 6JH8 "sheet-beam" demodulator tubes; I can remember an old TV commercial from the early 60s boasting of "Zenith's patented color demodulator".

I always thought that the '62-'72 Zeniths had better color than the RCA sets; if you watched a football game on a Zenith, the field was really green instead of a blueish-green.

I worked for a Zenith dealer 25 years ago, and worked on most of their tube color sets. Charlie's picture tube is a rebuilt tube; if it is a Zenith it was probably installed by a Zenith service dealer. The 29JC20 and the later tube Zeniths were much easier to work on than some of the other makes.

[Charlie]

Nasa,

VDC in Dallas will rebuild your 21FBP for 165 bucks (not including the shipping). Their phone number is 800-323-9278. Ask for Phil.

He really doesn't like to ship these, but he has come up with a way that he feels will get the tube back to you safely in one piece.

Keep in mind... due to the nature of these tubes being 40+ years old, he will not guarantee you the rebuild will be successful. He has done many 21FBP's for a few of us here on AK with mainly excellent results. But, there has been a failure or two... usually the glass cracking while in the oven. So, it's kinda a gamble on your part. So far, I have brought him 4 duds and 3 of them were a success. He is also currently rebuilding another 21FBP for one of our west coast members.

Phil can give you all of the details when you speak to him.

Good luck!

[Eric H]

Charlie, if the rebuild fails or the tube breaks do you still have to pay the full $165?

Eric

[Charlie]

Originally posted by Eric H
Charlie, if the rebuild fails or the tube breaks do you still have to pay the full $165?

Eric

Yes, that's the only bad part. He made that clear to me.

However, I had one of my tubes regunned, and it turned out that the new gun itself had a short. In this case, they will try again without charging for it.

[nasadowsk]

Hmm, I'll have to look into that.

Now - when was the 25LC20 chassis made, anyway? Was this early or late in Zenith roundie land? I know pre '64 - the set doesn't have UHF at all (but a click stop for it, but hey! someone stole the strip in that slot!). Oh yeah, any help on what a good sweep generator/marker setup is - mine seems to suck

Actually, any hints on getting the alignment would be useful, mine's almost right in B&W, but I'm getting that 'echo' effect on vertical lines, (i.e., a few lighter repeated lines next to it - should I keep plugging away at the alignment, or am I really seeing something in the Y amp that's messed up?). And no color when set for a nice clean B&W pic. Actually, I can get darn near amazing B&W reception on it. But hey, it's a color TV! I want my color, too!

As far as tackling this set capacitorwise - it's got a LOT of those early 'brown drop' epoxy capacitors - like Orange Drops but brown. Are they in the Black Beauty catagory, or are they ok? I've only got a few BBs and such in this set...

Better color than RCA? I'll have to wait until the tube's rebuilt. I'm not sure if this thing's rare earth or not - the screen's that dark green tint when off, and the reds aren't orange on this set. The RCA next to it? Reds so red they're orange...

Sigh...I'm getting there, slowly, I guess...

[Charlie]

This is something handy that Doug had posted some time ago...

Just so you know, zenith followed a chassis date pattern, in which the first letter in the chassis represents the year of the chassis, like "20Y1C48", in which "Y" is 1968, so:

M 65
N 66
X 67
Y 68
Z 69
A 70
B 71
C 72
D 73
E 74

Although Doug's list starts at 65, it would be safe to assume that the following would apply:

J 62
K 63
L 64

Nasa, you mentioned your set not having a UHF tuner. Did they become standard equipment part way thru 64? Your chassis could be a very early 64 model.

Is your CRT the A version? 21FBP22A? IIRC, isn't the 'A' supposed to signify improved brightness and rare earth phosphors?

[Jeffhs]

Originally posted by nasadowsk
Hmm, I'll have to look into that.

Now - when was the 25LC20 chassis made, anyway? Was this early or late in Zenith roundie land? I know pre '64 - the set doesn't have UHF at all (but a click stop for it, but hey! someone stole the strip in that slot!)

I'm not at all sure, but maybe there never was a strip for the UHF position in Zenith TVs made before 1964. I once had a Sams Photofact for the 25LC20/Q (the Q after the model number denoting Space Command remote equipped); the picture of the set on the front of the folder seemed to be of the 25LC20, VHF only.

Generally, the only way to get UHF channels on any TV made prior to April 30, 1964 was to use a UHF converter ahead of the set's own tuner. The VHF tuner was set to channel 5 or 6 to receive the converter's output (whichever was an inactive channel in the set owner's area--either channel 5 or 6 are always unused in any TV market, since the two channels are adjacent to each other) and all UHF tuning was done at the converter.


Some markets, such as Fresno, California, Fort Wayne, Indiana, Youngstown, Ohio, et al. (areas which got their TV stations after the FCC quit issuing new VHF licenses), only had UHF TV channels and still do today. Back in the '50s, when these stations first went on the air, TV receiver dealers in those cities marketed specially-built all-channel sets (and, of course, converters for older VHF-only receivers) before they were available in markets with only VHF stations. I grew up in a suburb of Cleveland and remember when the city's first UHF station (PBS channel 25) went on the air. The year was 1965 and we had just gotten a 17" Sears Silvertone all-channel b&w portable TV. While the VHF reception from our three network stations (channels 3, 5 and 8 at the time) was good, reception on channel 25 was terrible in our area, which was about 30 miles southwest of the transmitters. I later found out what part of the problem was, while watching channel 25 sign off one night; the PBS channel was only running 1 megawatt ERP, and we were trying to watch it just using a UHF loop antenna in our near-fringe area!

BTW, I now live in a definite fringe area for all VHF TV channels and FM stereo radio (45 miles from the transmitters) and have cable for TV, as does just about everyone else here in my small town. The irony of it is, however, that all four of Cleveland's UHF channels (except PBS 25) come in here just great, using rabbit ears. I have discovered as well that the PBS channel I had such problems with back in the '60s (again, channel 25) now has a translator station just about five miles or so from my hometown, and another one not too terribly far from where I live today. I guess translators aren't dead yet.

[Charlie]

Finally got the verticle roll to stop. Two black-beauties, although they checked well within specs, evidently just couldn't do the job. They were .01 1000v caps, and while i didn't have any in orange drops, i did find a couple of .01 2kv disc capacitors that i stuck in there. Seem to be holding the picture just fine.

One problem fixed... many more to go! Progress... at least I am making progress!