Ed Stone
Forum Participant

How hot is ‘hot’. If it is too hot to hold your finger on (>60C) then it is probably running on the hot side of what it should. Some possible reasons for this:

– you are running a 110v primary tap on 120v on a transformer that was working close to its rating (can be a problem for many sets). Can be solved with a shunt transformer, dropper reisitor or back to back zener diodes in the primary circuit;

– there is a fault in the transformer (shorted windings) – check to see you have approximalely equal AC voltages on either side of the HT secondary winding (if not, likley some windings on the lower voltage side are shorting, causing the overheating). Heater windings rarely short;

– there is a fault in the set: most likley a very leaky smoothing capacitor(s) in the power supply or faulty recifier tube – check the HT current draw