Obnoxious hum on Bogner Shiva 20th Anniversary head

  • Thread starter Thread starter derrek_clay
  • Start date Start date
derrek_clay":1ed97lki said:
Gotcha, gotcha. Haha I might use something other than my hand to bend down the caps, just in case.
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I wouldn't. You don't want to break the legs off. You can feel with your hands. You will be safe. Try your fingers first in the area.
 
Okay, cool. Bend them back toward the direction of the front knobs? or back toward the rear? There's some wiring in the way if I bend them back toward the rear. I touched them and didn't die, so that's a good start at least haha
 
derrek_clay":2oxuyvf4 said:
Okay, cool. Bend them back toward the direction of the front knobs? or back toward the rear? There's some wiring in the way if I bend them back toward the rear. I touched them and didn't die, so that's a good start at least haha
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Toward the rear. May as wekkll try it rather than putting your fingers in a hot amp. Not promising anything. It worked for me. It did not make it go way but greatly diminished it and I didn't worry anymore after that.
 
Okay, so this looks to be about as far as I can bend them down before the rear one starts to rub against the orange wiring and the front one starts to rub against that red wiring. Is this far enough? Or will they be okay against the wiring, and I should bend them further?
 

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derrek_clay":3751ko6p said:
Okay, so this looks to be about as far as I can bend them down before the rear one starts to rub against the orange wiring and the front one starts to rub against that red wiring. Is this far enough? Or will they be okay against the wiring, and I should bend them further?
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See if it helped with the hum. If not I would bend them back. I do think it is emf but yours could be in a different area. Could be closer to your PI out caps. Couldn't hurt to try
 
Didn't seem to help too much with the volume of the hum. It might have been a bit quieter when the caps were lowered, but not much. But I think you might be onto something. The hum sounded slightly duller when I bent the caps down and the pitch of the hum went slightly lower.
 
derrek_clay":292eug4g said:
Didn't seem to help too much with the volume of the hum. It might have been a bit quieter when the caps were lowered, but not much. But I think you might be onto something. The hum sounded slightly duller when I bent the caps down and the pitch of the hum went slightly lower.
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A tech can scope it and figure out where it is injecting.
 
Lets hope so. Given all the info I have now, maybe a tech can better isolate the issue and finally get rid of the hum. Third times the charm, after all. If that doesn't do it, I'm gonna be left with no other choice but to sell the amp. I'd hate to do it, but I just can't live with the hum.
 
Great thread with awesome RT support!!

The fact the hum vanished when the PI bottle got yanked at least localizes which half of the amp the problem is stemming from. If the PI socket gets pulled and the hum vanishes, that's indicative of a preamp section problem - because whenever I've had transformer or power section issues, the noise still persists when that PI bottle got pulled.

Anyway - sounds like we've got a solid handle on what's happening here and I hope it gets remedied quickly for you and your Sheevs. They're great amps!!

Mo
 
Maybe I missed it but has it always been this way? Did it just happen one day out of the blue? If it did happen out of the blue, was there anything you had done recently like swap a preamp tube? Do the tone controls affect the hum?
 
Dc leak to pi grid through a bad coupler maybe? You said pulling the pi made it go away.
 
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