Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: ronco05 on April 07, 2012, 07:35:27 am
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I recently rebuilt a totally trashed 74 Orange OR80. The amp sounds great but i get a hum from one of the transformers. Is this normal? The hum is not transferd to the speakers but its pretty loud.
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My '74 Orange OR80, which came to me trashed, also has a humming PT------ it did bother me but it's not noticible while playing the amp----- it's been this way for several yrs now and nobody else has ever mentioned it while playing the amp------ one guy brought another '74 OR80 to me that had problems and after playing mine said, "Make mine sound like yours !!!"--- so i don't worry about it anymore.............................gldtp99
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thanks for the reply.
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Haha, I had a '74 Orange with the same problem - I don't believe it! I tried a lot of things: isolating the PT with rubber from the chassis, shimming the core with wood, and replacing the bolts that held the lamination together (the plastic isolation washers had become brittle and cracked). Nothing worked. I got a replacement PT from Heyboer... same hum!!! The hum was coming from the PT! I ended up selling it to a guy. I later saw him and asked if he got rid of the hum, and he said that he had! I asked him what he did, and he said that he just went through the schematic and returned everything to stock (there had been some caps replaced etc, but nothing major, and that was it. I couldn't believe it.
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I think he was fibbin'. ;)
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Yeah, I don't know because it totally had me stumped. He's a tech that won't do anything to an amp until he meticulously goes through the schematic and makes sure everything is stock. I wish I had that type of patience, but I was so convinced I knew where the problem was because the amp sounded fine otherwise.