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I used a voltage-bucking transformer on my Harman-Kardon A300 with great success. This amp runs the tubes pretty close to the max voltages and I was also having a problem with output tubes arcing due to high line voltage (and therefore high B+ voltage). I used an old power transformer from an XL-100 color TV and was able to find a winding that would buck the AC line about 6 volts down.
I have seen some really bad damage done by the lack of fuses in some equipment, particularly Hammond organs. Yes, even new capacitors or tubes could short out although a lot less likely than old electrolytics, so I always put fuses in when I repair something. I have seen burned up wiring and power transformers and 5U4 tubes where the glass melted due to a short. The 15-20 amps available from an AC wall outlet can do a lot of damage when a component inside an un-fused unit shorts and the house circuit breaker will not blow.
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