Merry CTC-5 Christmas 2020

[old_tv_nut]

The set has always been dim. It was pretty dim with the glass CRT and is dimmer now with the 21AXP22A. However, I feel it may have drifted dimmer with time and may need some TLC to perk it up a bit (but not expecting miracles.)

Besides all the other low-performance issues with this chassis, insufficient luma drive seems to be one. When I have attempted to increase the video level with AGC adjustment, I reach a point where the AGC locks up after changing channels and have to back it off. (I don't recall for sure, but I think this is mentioned in the service info).
The set has aways had way more chroma demod output capability (CRT grids) than is needed to match the cathode drive for proper color saturation.

In making the photos, I noticed that the stills from the adapter on channel 3 were brighter than the movies played from a DVD player into the UHF modulator (a little Chinese-made unit). Not sure if the UHF modulator is undermodulating a bit or what.

I am thinking about retubing the video section, as I definitely have noted before that the video output amplitude in most tube sets is dependent on the gain of the final output tube. In the '67 Magnavox I had, I bought a number of video output tubes and tried them one by one until I found the strongest. It made a big difference, with the CRT looking tired to looking brand new.

I also have noticed in the past that the set seems to be crazy sensitive to replacement of IF tubes, some tubes apparently producing some oscillation or something that totally messes up the picture. Never did figure that out, just substituted tubes until I got a set that works. This, of course, could have some relation to the AGC range.