Today's Mystery Guest (RCA CTC-4)

[Phil Nelson]

Thanks, I replaced the horizontal output tube right after I fixed the horiz oscillator.

Earlier today I started scoping things in the chroma circuits. Since it's doubtful whether the IF section is passing a color signal, I disconnected the output from the video detector and injected a video signal from the pattern generator at the video amp grid. With luck, I can get some clue whether the chroma circuits are operating.

The waveforms on the burst keyer tube look pretty normal. Here's the burst keyer grid (pin 9):



Here's the burst keyer plate (pin 1):



Here's the burst keyer cathode (pin 8):





I also scoped the bandpass amplifier, demodulator driver, color killer, blanking amp, and G-Y/R-Y demodulator:

http://antiqueradio.org/art/temp/RCA...ndpassGrid.jpg
http://antiqueradio.org/art/temp/RCA...DriverGrid.jpg
http://antiqueradio.org/art/temp/RCA...KillerGrid.jpg
http://antiqueradio.org/art/temp/RCA...ingAmpGrid.jpg
http://antiqueradio.org/art/temp/RCA...ulatorGrid.jpg
http://antiqueradio.org/art/temp/RCA...atorOutput.jpg
http://antiqueradio.org/art/temp/RCA...ulatorGrid.jpg

I haven't pored over all this yet, but I get the idea that some of those circuits are operating, anyhow.

Phil Nelson