This weekend I got an RCA CTC-48 combo from 1972. The CRT plastic cup on the back was broken at the thrift store but CRT appears to be OK.
It's labeled "Accu-Color Solid State" does not say XL-100, however it is the upright modular chassis just like the XL-100. The control panel looks like a late model CTC-39.
Have power but no light on screen. When I discharged the HV there was no spark and there does not appear to be HV AC at the lead from the flyback to the tripler.
Tried reseating the Horiz. module which appears loose, but no change.
There is a whining sound from the flyback which changes pitch with the Horiz. control so it appears the oscillator is working. It's been a while since I did any serious troubleshooting on one of these models, any common trouble points to watch out for?

Did you check the HV AC to the tripler with the wire disconnected?
A shorted tripler would kill it I think.

Thanks Eric, I will have to try it. The last of these type of sets I worked on (CTC-68) had problems with the tripler on it. Will have to see if Moyers has one, have not ordered from them before but really need to.

If memory serves me correctly, RCA sets of that era used a horizontal sweep system based on two SCR's, the "trace switch" and the "retrace switch". Along with two damping diodes that work with them, many high voltage difficulties can be cured by checking and replacing these SCR's and diodes, as necessary.
Good Luck!