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Old 05-13-2015, 04:57 PM
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Phil Nelson Phil Nelson is offline
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Okay, I see your point about the self-biasing.

I'm using a newish Fluke digital DMM. The alignment instructions specifically state that you must use a VTVM to measure the -10V at pin 6 of the oscillator. It's certainly a sensitive spot. Later in the alignment instructions, they tell you to temporarily disable the oscillator by connecting a 1-foot piece of wire to pin 6. Connecting a short piece of wire does indeed disable the oscillator, so maybe it's quitting when I try to measure that voltage.

I posted the page with the alignment procedure here for reference:

http://antiqueradio.org/art/RCACTC-4...tProcedure.jpg

At this point, I'm more concerned about output from the transformer than whether the oscillator is running.

Step 3(a) says that a peaking response to adjusting T115 shows that the oscillator is running AND T115 is passing the signal. I am not able to find a peak, so I gather that one of those conditions is not true (for instance, maybe the oscillator is running, and T115 is passing a sort-of signal, but the signal is weak or dirty).

Step 3(b) tells you to check for negative voltages at pins 2 & 7 of the R-Y/G-Y demodulators. I find about -20V at pin 2 and a smaller negative voltage (-10 to -15V) at pin 7.

In step 4, I am able to find a peak when adjusting L125, the hue coil.

In step 6, the adjuster for T112 runs out of room before I find a peak in the voltage.

So, running through the procedure is a mixed bag. Some adjustments work, others don't. The end result is a TV that can lock colors with difficulty on a very strong injected video pattern.

Phil Nelson
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