Schu Posted May 15, 2017 Share Posted May 15, 2017 So a friend of mine built a kit 300b tube amp and it's begun to shoot sparks out. He said it happens when he taps on one of the output transformers. He recently upgraded the capacitors to jupiter and replaced all the 6sn7's and 300s, but he doesn't think that is the issue. the amp is many years old and has always worked fine until this latest episode. Any ideas? Quote Link to comment Share on other sites More sharing options...
Schu Posted May 15, 2017 Author Share Posted May 15, 2017 He also said one channel went out prior to seeing sparks... is a transformer dead? Quote Link to comment Share on other sites More sharing options...
Schu Posted May 15, 2017 Author Share Posted May 15, 2017 He solved it... one of the other caps was touching the bottom cover... where it was arching. which is surprisingly steel. Quote Link to comment Share on other sites More sharing options...
richieb Posted May 15, 2017 Share Posted May 15, 2017 Now with the problem found/solved my suggestion of a fire extinguisher is now no more than the smart assed remark as originally intended - Quote Link to comment Share on other sites More sharing options...
Schu Posted May 15, 2017 Author Share Posted May 15, 2017 Well... it's dead again. I have a picture Quote Link to comment Share on other sites More sharing options...
mike stehr Posted May 15, 2017 Share Posted May 15, 2017 Obviously the cap is still shorting against the bottom cover. Either figure out how to shorten those screw terminals on the capacitor, or maybe lower the cap within it's clamp. Or...raise the bottom cover enough (with shims or whatever) to clear the capacitor terminals. Quote Link to comment Share on other sites More sharing options...
Don Richard Posted May 17, 2017 Share Posted May 17, 2017 That's some lousy soldering on that amp. I am not surprised that it has issues. Quote Link to comment Share on other sites More sharing options...
Schu Posted May 17, 2017 Author Share Posted May 17, 2017 I won't tell him that. He's a tinkerer and build the thing himself. It seems to be working again... Quote Link to comment Share on other sites More sharing options...
babadono Posted May 17, 2017 Share Posted May 17, 2017 A small piece of some type of insulating material on the inside of the bottom cover where the cover and that capacitor come in contact intermittently seems in order. Or a nylon screw? Quote Link to comment Share on other sites More sharing options...
mike stehr Posted May 17, 2017 Share Posted May 17, 2017 On 5/15/2017 at 3:26 PM, Schu said: Well... it's dead again. I have a picture The Dale resistor in the upper left hand corner appears to need the right side lead soldered to the terminal strip. If you look at the image full size, it looks to be soldered very lightly or not at all. It could be just the way the image appears, however. Quote Link to comment Share on other sites More sharing options...
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