Raster
 

Using a variac, I was wondering what the "average" voltage would be before I can see raster (snow) on a '56 Rca ctc-5. Its the Wescott model.

There really is no definitive answer to that, it's all very subjective to many things, like how long the set has been sitting idle, the health of the components, tubes, caps, etc, each “resurrection” will behave differently.
If you want a baseline, you can always watch some of shango066' videos on youtube, he has done it many times with various sets, including roundies, it can give you an idea of what to expect.

I started getting a raster at around 90 volts on my westcott.

90 VAC is probably the average for all sets Over all condition of
the PS/hoz / HV / CRT will have a great effect.
On newer SS sets you may not be able to start the set due to the
start circuitry. In that case after a successful start you can
turn things down to about 90V. Zenith CC2 sets I have run down under
90V & still had a very watchable pix but unstable ( breathing etc).

73 Zeno:smoke:
LFOD !

I never use a variac. I never plug a set in that is more than 50 years old until it has a full check with chassis out. My CTC5 had a thorough vetting first.

I will alway check and reform or replace the electrolytics and change initially the obvious papercaps that will be stressed with a high DC.

It's not worth it.

Like Penthode, I just don't bother powering up before I swap the filters. Experience has shown it to be futile. Maybe I'll bring it up slowly over 30-60 seconds after the recap, just in case something goes kafrizzle!