[Phil Nelson]

I'm debating where to go next. I have replaced a number of marginal resistors, without any dramatic improvements. When injecting a video signal, I am able to get stable color bars (with wrong hues) by working through the entire color AFC alignment procedure on page 22 of the RCA service clinic manual.

However, in step 3, I am not able to find a voltage peak when turning the bottom adjuster of quadrature transformer T115. The voltage increases in one direction until the adjuster hits the wall. And I am still getting only zero volts on pin 6 of the chroma reference oscillator (V124A) rather than the desired -10 volts. Likewise with adjusting T112 (bottom) in step 6: I don't find a peak -- the voltage increases in one direction until the adjuster stops.

My sense is that the color AFC system just BARELY works at all, and only with a very strong color bar signal from a generator. When I switch to normal program content, things fall apart. The colors are all wrong and the image is poorly focused.

I have a replacement transformer, but it's not identical to the original. Instead of a 1000-pf cap in parallel with each secondary coil, it has a 1500-pf cap paralleled by a 680-ohm resistor. Maybe it's a plug-in-play replacement, maybe not. Its example circuit is taken from the RCA CTC-2B, which uses an amp between the oscillator and the transformer.

I'm debating two options:

1. Just stick in the new transformer and see what happens. (Pro: maybe it'll work. Con: the replacement is not easy, and if I wreck either the old or new transformer in the process, I'm worse off than before.)

2. Breadboard the CTC-4 oscillator circuit using the new transformer. (Pro: if it works in the CTC-4 circuit without modification, then we're home free. Con: if it doesn't work, then I'm torn between modifying the new transformer or trying to rewind the old one, and if neither of those options works, then I have a completely dead TV.)

Since I don't have standalone power supplies, perhaps I could power the breadboard circuit by tapping into the CTC-4's 6.3VAC filament circuit and +285VDC B+ circuit. It needs about -10VDC bias voltage; perhaps I could tap into the CTC-4's -20VDC supply and shunt some of that to ground with a pot.

Or, I could throw a tarp over it and work on something else, but it bugs me to leave the TV in this half-baked condition.

Edit: re breadboarding, I have an additional concern, which oldcoot_88 alluded to earlier, that it might seem to work on the workbench -- that is, the oscillate might oscillate and the transformer might pass a signal -- but the output might not be right in phasing & amplitude for the CTC-4.

Phil Nelson