Check ohms of any large resistors in the power supply circuit. Be sure the electrolytics are in there correctly with respect to + and -, and pull the rectifier tube, leave all other tubes in place. Use a dim bulb arrangement, say a 60 watt bulb in series with the power cord. If the bulb stays dim, you're probably OK.
If normal brightness, xfrmr primary may be shorted.
Let's assume dim bulb. Remove dim bulb and plug set into variac, bring up easy to normal voltage. All tubes should light, but of course no sound due to rectifier being out. Feel power transformer. If after 20 minutes
it's still just warm to touch, you're OK. Turn set off, plug rectifier back in, off you go.
Watch/touch/sniff carefully for a while in the power supply area.