Today's Mystery Guest (RCA CTC-4)

[wkand]

If the video amp is after the tuner, signal path wise, why would a weak picture(while injecting at the control grid of the video amp) mean that the tuner was bad? Not saying it isn't, I'm just not following the sequence of events I guess.

[Phil Nelson]

I was just walking backward, doing a very basic check to see what sections could pass a signal. Seeing a picture when I injected video at the video amp suggested that things downstream from there were working (at least marginally). Seeing a picture when I injected an IF signal at the IF amp suggested that things downstream from there were working. So, the no-signal problem was likely between the antenna terminal and the IF strip.

The solution was simple, after all, and it turned up when I serviced the tuner. The UHF-VHF switch in back of the tuner was funky and it had stuck in the UHF position. Here is the switch working normally:



I'm not impressed with that switch, or the quality of the tuner in general, but it's all clean and operational now, and I can get a picture through the antenna input.



And now for that Wizard of Oz photo you've been waiting for!



Yah, we're a long way from a good color picture, but the CRT transplant was successful, knock on wood, and I think there's hope for the old girl, after all. Now to read up on CTC-4 setup procedures . . . .

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html