Working on First GE Color

[bgadow]

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

[NewVista]

Originally Posted by bgadow

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 !

[jr_tech]

Wow! Great work, thanks for all the pictures!

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

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

[bgadow]

Originally Posted by jr_tech

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

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

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.

[NewVista]

Originally Posted by jr_tech

1. Is there room inside that huge cabinet to actually mount the 21" jug up to the bezel in a somewhat normal position temporarily ?
jr

An interesting thought.
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.

[old_coot88]

Originally Posted by NewVista

Surprisingly this set uses simple burst-excited crystal for phase locked subcarrier...

Um.. not tryin' to be picayunish, but wouldn't that be phase-locked referance oscillator?

Bill(oc)

[stromberg6]

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

[old_tv_nut]

Originally Posted by old_coot88

Um.. not tryin' to be picayunish, but wouldn't that be phase-locked referance oscillator?

Bill(oc)

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.

[old_coot88]

Originally Posted by old_tv_nut

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.

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

[NewVista]

Originally Posted by old_coot88

..it doesn't use a 3.58 reference oscillator at all, right?

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.

[old_coot88]

Originally Posted by NewVista

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)