Prototype set is here

[Penthode]

I came across another article entitled "General Color-Receiver Design Considerations" presented at the fall meeting of the IRE and RTMA in October 1952 by staff at Hazeltine Labs. It is a description and details on CPA receiver design.

On the final page of the article is a complete diagram of a CPA demodulator. The color oscillator has no crystal! A 12AT7 is used: one half the reactance control and the other half a Colpitts oscillator. Only LC components and no crystal.

I will try and post the drawing and article tomorrow. But the decoder line up in the drawing includes the following:

12AT7 Reactance/3.89MHz Oscillator
1/2 6AL5 Clipper
6CB6 Bandpass amp
6AS6 B-Y demodulator
6AS6 R-Y demodulator
1/2 12BH7 B-Y matrix amplifier
1/2 12BH7 R-Y matrix amplifier
1/2 12AT7 G-Y matrix amplifier
6CB6 Isolation Amplifier (or Color oscillator buffer output)
1/2 12AT7 Field Recognizer Driver
1/2 12AT7 Field Recognizer Phase Detector
12AT7 CPA Multivibrator
1/2 12AT7 Field Recognizer Keyer