RCA CTC-28 repair

[Chad Hauris]

Today I have been working on an RCA CTC-28 I got from an estate sale a few months ago. I replaced the electrolytic capacitors and rectifier diodes and bypassed the degaussing thermistor as it had fallen apart. Also I relocated a wirewound resistor to the front of the chassis which had burned up wiring due to heat and replaced the burned wiring, and put a fuse in the power line input.

When I powered it up for the first time I got a raster but no picture or sound. I substituted the RCA tuner with that from a Zenith set hooked up to an isolation transformer and still didn't get anything but when the RCA tuner was hooked up to the Zenith set I got a good picture.

I then used the Zenith tuner IF output as a test signal source through a 100 pf capacitor and applied it through the IF stages of the RCA and found that it wouldn't pass through the last IF stage but there was weak sound when the signal was connected to the output of the last IF. It turns out the last IF tube was bad and when I replaced it I got good signal.

Then I did some modifications to the chassis consisting of using the power switch to control a 110 VAC coil relay to remove the high current load from the set off of the power switch. I added a terminal strip connected to the regulator 1000 ohm resistor and the horiz output cathode so I could test those easily with the chassis in the set and put in a fuseholder in the horiz output cathode for a 300 ma fuse.

I now have a pretty good picture with color but could use a little more contrast and to set up the purity. I measured the horiz output cathode current and it is 210 ma.

Here are some videos of the repair process:

Part 1: http://www.youtube.com/watch?v=L-bJ8IGz9Fg

Part 2: http://www.youtube.com/watch?v=z6ll5ByKAiU