Here's why I ask:
Upon powering on my ST-120, I heard a slight crackle and the rectifier arced. The fuse was blown as well. I replaced the tube and fuse and again saw the rectifier arcing then the fuse blew. (It was not a known good rectifier used to replace the first one.)
I re-flowed the solder on the cap*, replaced the fuse and inserted a new Sino 5AR4. The amp works fine now. Typical voltage at my house is 117 - 120V.
* I had replaced this several months ago and it being the most recent change, thought it might be the problem.