I have a VTA-120 that had a problem this morning. I powered it up this morning, and when the Time Delay Relay timed out and applied power, I heard a "Chunk" through the speakers, and the fuse on my Variac blew. I replaced the fuse, turned the volume to off, tried again, this time watching the amp. TDR time Expired, "Chunk", and a power tube flashed. Blew a Variac Fuse again. I am going to pitch this quad of tubes, order some more fuses, and order another matched quad. Will probably open up the Amp, do a visual inspection for blackened parts, swollen capacitors, etc. and do the Voltage checks from the assembly instructions. Anything else I should do before powering up the Amp again? I have noticed for awhile that the lights briefly dim whenever the TDR relay kicks in.
Without the Amp plugged in, my Killa-Watt, plugged into the Variac, reads 118.8 -- a reasonable voltage.