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Hey guys, first time on this forum. Here's my situation:
I built a guitar amplifier as an Orange clone a couple years ago and have been using it since, modifying it as time and my imagination allows. The amp is nothing like an Orange now, and all components have been replaced on the amps save the transformers and chassis. Problem is, there has ALWAYS been a problem with this amp humming, and the hum increases/decreases when I take the ground wire that is connected from the cathode resistor to it's grounding node, which is the cathode of the decoupling capacitor for that stage. Sounds like 60 Hz. When I make the cathode ground with super long (like three feet!) and make shapes with it out side of the chassis then the hum sometimes goes away, so this leads me to believe that the hum is induced, BUT, why would it only be induced on the second preamp stage, and why on the cathode ground wire? i don't understand. Another strange thing: the hum used to come on go as the FIRST preamp stage cathode wire was moved, but after I removed the 68 k grid stopper the hum has since moved to the second stage. I can do lead dress to reduce the hum a bit, but not completely. anyone got any ideas?
thanks, Anson
I built a guitar amplifier as an Orange clone a couple years ago and have been using it since, modifying it as time and my imagination allows. The amp is nothing like an Orange now, and all components have been replaced on the amps save the transformers and chassis. Problem is, there has ALWAYS been a problem with this amp humming, and the hum increases/decreases when I take the ground wire that is connected from the cathode resistor to it's grounding node, which is the cathode of the decoupling capacitor for that stage. Sounds like 60 Hz. When I make the cathode ground with super long (like three feet!) and make shapes with it out side of the chassis then the hum sometimes goes away, so this leads me to believe that the hum is induced, BUT, why would it only be induced on the second preamp stage, and why on the cathode ground wire? i don't understand. Another strange thing: the hum used to come on go as the FIRST preamp stage cathode wire was moved, but after I removed the 68 k grid stopper the hum has since moved to the second stage. I can do lead dress to reduce the hum a bit, but not completely. anyone got any ideas?
thanks, Anson