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| | |-+  JCM 800 2204 Squeal		 « previous next »
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Author Topic: JCM 800 2204 Squeal  (Read 5617 times)
rez667
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« 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
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cmoore
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« Reply #1 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
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rez667
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« Reply #2 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
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rez667
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« Reply #3 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  Chair Dance


thanks again for your help Smiley


rez
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