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Not sure of the vintage of yours, but there are not a lot of paper caps in this one. The whilte elmento tube caps are the ones that may cause trouble but chances are they are ok. They are rated 1000vdc think there are 4 in there total.
The can caps are often fine. If the HOT is red plating the most likely cause is no grid drive since that is how it gets its neg bias. As a min you should check the cathode current, should be around 210-220ma(I use a socket that plugs into the socket, and has leads where the cathode is for connecting a meter) of the HOT, AND check the 6BK4 cathode current (there is a test point for connecting a volt meter so mearuse the voltage drop, should be around 1vdc drop), AND check the HV with a prob, should be around 22-23kv.
all those are related, if not working then I would start by checking the horz osc tube, its a triple triode compactron, if its defective there will be no drive to the HOT and red plating will occur. Sometimes you just need to wiggle the tube around some.
For general checking out of B+ I pull the HOT out of the circuit completely. I read somewhere that just disconnecting the plate lead is not a good idea, cant recall why.
With it pulled you can check the B+ current draw, should be very low. I generally do this with a metered variac, I pull the hot out, and the vert out, then do a very slow powr up. the variac I have has a voltage and currrent meter so I can see whats going on. Start slow and watch for current. I start out at 10vac just to see if the PT is shorted, then slowly ramp up to about 60-70vac over a period of time, again watching the AC current, again with out the HOT in it should be very low, around 500ma IIRC by the time I got to 70vac. I stop there since with no HOT load the B+ will go higher than the rated voltage of the can cap (I monitor the B+ voltage as well with a DMM while doing this, stopping when I get to about 375vdc, which will be well below line voltage). If you are just pulling the lead from the HOT and plugging it in to full line voltage, then the B+ will surely overshoot the voltage rating of the can caps, not good.
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