Working on First GE Color
 

My recent project was with a GE 15CL100 chassis which I was able to restore to operation with the Wallace Manual available thanks to ETF & J. Folsom.

This set came from fringe suburban Milwaukee WI where according to owners it was one of 70 in an initial production run mainly intended as demo sets for favored GE dealers/locations. Since there was a pioneering color station here in '54, WTMJ NBC, this area got this one (or more?) demo set(s).

There are two schematics in the Wallace, "First Production" & "Second Production". The 2nd production has about a half-dozen minor circuit changes. I have not seen evidence of a 2nd production TV; I suspect production was halted in the anticipation of the coming RCA 21" kine to better complement this set's refrigerator-like cabinet.

As you might guess, the chassis is big and heavy (60 lbs) and consumes the best part of 500 watts. With a high tube count, there is high component density and many capacitors to change. However when paper caps are eliminated, it turns out to be a stable, reliable performer with a conservative, cool-running flyback transformer in a large well-designed HV cage.

There was some horiz AFC foldover on the right side that only upgrading to 2nd Production changes could correct.

Being from the days of pioneering experimentation, there are some peculiarities like the "Hue"(Tint) control being almost hidden (from customer tampering) on the chassis back panel.

Its 15GP22 RCA kine has good guns but too much accumulated atmospheric ingression for effective operation (needs to be re-vacuumed one day)

Zowie, an interesting project. What sort of 21" CRT did you use in that workbench setup?

Phil Nelson

Nice going Colin! Please tell us the story of how you came to be aware of this set in the possession of the former owners.

Presently I am working on the Helium Leak detector mass spectrometer so maybe some day we will be able to locat the leak in that gassy tube.

It's a 1960's Zenith with metal band/lugs & implosion faceplate. Has large neck of roundies that's more compatible with 15GP22 yoke. Socket connections had to be extended (don't have a 15GP22-to-21" adapter/extender).

Hi Bob, That's great. The experiments you guys are doing are making a valuable contribution to the science and progress of this important endeavor of historical discovery & preservation.

Wowie zowie! That's incredibly cool. :cool:

It would be quite a long time before GE would engineer/build such a fine set again! Great to see this one alive.

Surprisingly this set uses simple burst-excited crystal for phase locked subcarrier (a feature of minimalist 60's designs like the PortaColor). Works excellently.

The HUE control with a knurled brass knob can be seen hidden from the customer (for good reason?) on lower back panel. It's a shielded vari-cap that rotates continuously.

Twin "Coke Bottle" 6CD6 Horiz O/P only draw a meager combined 1/5-A

Now have CTC-5 hooked up to Zenith Test CRT (2nd pix) - it's more trouble than the GE !

Wow! Great work, thanks for all the pictures! :thmbsp::thmbsp::thmbsp:

The pix of The neck glowing did, however bring back a rather unpleasant memory, when the CRT in my avatar died. :tears:
Seeing the chassis hooked up to a 21" (fat neck) tube and producing a fair picture raises some questions. :scratch2:

1. Is there room inside that huge cabinet to actually mount the 21" jug up to the bezel in a somewhat normal position temporarily ?
2. Any possibility of a simple add-on convergence driver so that the magnetic convergence coils could be used in a set designed for electrostatic convergence?

Not to suggest something that some might consider as egregious as fish-tanking on a super rare set, but seeing this chassis operating with the 21" jug suggests some interesting possibilities.

jr

Um.. not tryin' to be picayunish, but wouldn't that be phase-locked referance oscillator?
:o
Bill(oc)

I've known about the 15CL100 for years, and have a copy of a schematic, but this is the first time I've seen actual photos and screen shots of that receiver outside of the pic on the ETF website, and other similar pics. Thanks for posting all the info and pics, I really appreciate it! GE's approach to a color set is certainly different from RCA's, and is a great illustration of the history of the art of early receiver engineering and design. The crystal ringing circuit was used in a few other sets later, a Motorola comes to mind. Saved a couple of bucks over a complete oscillator/AFC circuit, I guess.
Kevin

This refers to a crystal "ringing" circuit. It actually does not oscillate on its own, but has a very high "Q" so that it produces a decaying oscillation that lasts longer than 1 horizontal line when excited by the burst. When this decaying waveform is amplified and clipped, it is sufficient to drive the demodulators.

I've wondered about this but never read a solid response. Roundies could be used with later rectangular test jigs, right? Should be plenty of room to fit something in there, though producing a correct picture might be very difficult.

Son of a gun. Then it doesn't use a 3.58 referance oscillator at all, right?

An interesting thought.:scratch2:
The 15GP22 appears to be mounted on a sub-board with bolts. Another sub-board with a 21 could perhaps be dropped in temporarily - without harming any of the cosmetics or construction - until 15GP22 situation resolved.

Yes, in the Wallace Manual you see a Burst-Gate, then a Hi-Q Crystal Tank Circuit, then buffer/clipper-limiter to deliver subcarrier phase-locked to Burst. I knew GE did this in the sixties but, as others have pointed out, Motorola and Admiral also sometimes used this ingenius idea.

Interesting. On a related note, in 1969 we pulled a (then) late model GE into the shop with a really bad color sync problem that couldn't be fixed in the home with tubes. Noticed an NE-2 neon bulb in the burst area of the circuit board and tried replacing that, and it fixed the problem. I don't remember the details of the circuitry as GE was not one of our store's specialty brands. But the NE-2 was involved in the burst gate circuit.
Bill(oc)

If I were in your shoes I'd try making a mounting for the 21" tube. I always thought that large mask arround th CRT was GE's way of saying " this was supposed to be a 21" set , but those slow pokes at RCA never supplied us with one ". I got to start scowering milwaukee closer, that is the second 54' color set in my area that I've missed! Finding one in the wild is the only way that I might be able to afford one in the next few years, and I'd really like to own a first year set.

Good luck on your restoration!

Tom C.

If you install a 21 inch crt in the set, and the picture only fills the center part of the screen like in the photo. Would you even need much dynamic convergence. That would be interesting to try to retrofit a 21 inch crt. Especially if it can be undone in the event of a breakthrough on rebuilding the 15Gs.

I thought it would be a good idea last night noting the detatchable 15GP mounting sub-board -- and then retaining the 15GP masking (as yoke underscans on a 21" to approx 15GP picture size). Cabinet Width is fine, but then discovered there is simply not enough height for a 21 (as big as the cabinet is)

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Does anybody know how many would pay a decent price for a rebuilt 15GP22? I wonder if the demand for them will ever be enough to produce any. It seems like there are enough sets in need to make it worthwhile.

If they have approx 2"dia neck that would be Dandy. Will keep an eye out

If you mean rebuilding old 15GP22 tubes, smart guys have been working on that for years without a perfect, affordable solution. Search this forum and you should find many discussions.

If you mean building new 15GP22s from scratch, the R & D expense would be insane. If this was possible at reasonable cost, it would have been done years ago.

Just my $0.02.

Phil Nelson

We are confident that RACS can rebuild them. The one they did a year ago is still going strong. I expect that within the next couple of months they will give us a price for the rebuild, which I expect will be over $1000. Even with shipping to and from France, I think this will still be a price that collectors will be willing to pay.

shipping costs?
 

The museum efforts at a rebuild are noble. Hopefully they will be successful soon. The rebuild price is expected, shipping it half way around the world has risks. What is the costs of shipping. A proper crate and packaging easily doubles the size of most things shipped international for protection. Can this double the rebuild costs?

Those folks at RACS do mighty fine work. Museum rebuilding would allow for in person drop off and pickup- for faster turn around while avoiding hazards of long distance shipping. I have not shipped anything overseas for a long time, oil prices makes this even worse now.

That is great! I knew you guys could do it! I would build a wooden crate for such a tube that could be dropped from 10 feet high on any side or top without harming it to be sure it could arrive safe. May be a bit costly but worth it and the container could be sold to each other person that needs a 15GP
I am so very impressed with all of you involved to hear the rebuilt tube is strong after a year. I think that is incredible!

My prediction if the myans are wrong bout 2012...
 

the economy will be great in a couple years and mint '54 RCA and all others that use the 15gp22 will go up to $15,000.00 .

I think those big neck rectangular tubes were 16 inch. 16CYP22 There must have been a lot more of those made than the 15 inch roundies. I heard that Conrac monitors used them as well as the Sears and Toshiba.

Cool, would like to find one, will be now tuned in to old portables at garage sales!

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