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Title: JCM 800 2204 Squeal Post by: rez667 on June 24, 2010, 03:00:30 PM I am having a horrendous time trying to trouble shoot this amp. When i turn the standby off there is a constant loud squeal. My plate voltage is 476V and i checked all the wiring going to my preamp and power tubes, I tried to change the pots, i switched the OT primaries around, to no avail. I am stumped.. any other suggestions would be greatly appreciated :-) I am going to buy new 12ax7's today.. Could this be a Xformer problem? please help. lol. i wanna rock this thing, and right now its a really expensive paper weight :-(
Thanks yall.. Rez Title: Re: JCM 800 2204 Squeal Post by: cmoore on June 24, 2010, 03:19:59 PM Tubes
Lead dress Presence circuit, wiring, component value Change ground location of speaker jacks Lead dress again.......Good Luck Title: Re: JCM 800 2204 Squeal Post by: rez667 on June 24, 2010, 07:17:41 PM just put new tubes in.. :-( didn't work.. I think i narrowed it down to the first EL34.. I'll desolder and resolder everything in the push-pull part.. :-( thanks for your advice m8.. I'll keep you guys informed.. hopefully it will help someone in the future :-)
rez Title: Re: JCM 800 2204 Squeal Post by: rez667 on June 27, 2010, 12:48:19 PM I ended up cutting all the wires out and rewiring it.. But it still made the same noise, but i heard a sizzling noise,
before it happened this time. I found that the pilot light enclosure was shorting to the chassis. So i unscrewed turned it on, and SQUEAL!!.. then i switched the OT primaries around.. and changed the grounding location of the 1 ohm bias resistors.. and it works.. my high input doesn't work, but that should be easy enough to fix.. I am just happy i actually heard my guitar outta it :chairdance: thanks again for your help :) rez |