Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Jim Coash on January 05, 2015, 12:35:13 pm
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Years ago I acquired a Sovtek Mig-50 amp. A friend who worked for ProCo in the rear of the old Gibson building on Parsons Street offered it to me as part of a deal. It seemed to work OK and I thought it sounded pretty good. A pair of 6L6s with a pair of robust transformers in a clean case. My son had a bass player at the time who fell in love with it so I sold it to him. Two years later he told me it was acting up so I offered to check it out. He seemed willing to trade it for an Ampeg rack mount solid state amp I had at the time and I decided to go with that. When I pulled it apart I found that two of the pots had been damaged beyond repair and instead of trying to find replacements I took the advice of another Sovtek owner and replaced all the pots (6) with new CTS units. That required a little surgery. I also found evidence of arcing around the two large filter cap cans next to the transformer. One can was grounded to the chassis, the other held off by a fiber washer that had broken. I ordered a pair of JJ radial caps in a slightly larger value and fitted them to the chassis. I used the schematic to re-wire them properly. The amp has a rectifier block and the rest of the circuitry looks OK. All of the tubes are relatively new, not original. Now I am ready to plug it into the Variac and see what happens. I wonder if any of you have advice on what else should be upgraded before I do. Jim
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I would fix it as is, replacing only parts that must be replaced to return to normal operation. Once I had a working amp then I would start musing over upgrades.