Backstory: A few days ago, I saw an ad for a local guy selling an early-version Ampeg V-4 for $200. I emailed him right away asking for details. Turns out there were two catches. 1. It didn't come with power tubes. 2. He was fairly certain the output transformer was blown. I told him I'd take it anyway. I figured it'd be a fun project. What it did was, 1/2 second after you flipped the power switch on, the 6A power fuse would blow. I tore it down the day after he dropped it off and couldn't find any signs of arcing, shorts, blown components, overheating, etc. The filter caps had been replaced recently so I was doubting those went bad. There were no power tubes in it and I took the preamp tubes out as well so a shorted tube wasn't causing the issue. There were no other defects I could find, visually. I told a friend of mine about it and he agreed to come over today with all of his testing equipment since he builds musical equipment for a living. He came over and poked around for about a half hour, testing the transformers (which, thank goodness came up with no shorts he could find) and tracing the flow of power through the amp. He decided it could only really be bad filter caps, bad rectifier diodes, or some freakish unknown problem with the output transformer. We started simple and desoldered all the rectifier diodes to check them out.. Guess what. TWO of them were shorted. Walked down the road, picked up a $2.50 worth of replacements, walked back, soldered them in, replaced the fuse, flipped on the power, and it powers up juuuust fine now. So $202.50 total + buying dinner and a beer for my friend for helping + $76 matched quad of replacement 7027A tubes = great deal on a V-4, if you ask me. I'm excited! Can't wait to try this out on the 4x12 I have coming this week!