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Epiphone Comet Tube Amp EA32-RVT


 :
11/21/1999 12:04 AM
Mike Gardner
 Epiphone Comet Tube Amp EA32-RVT
Epiphone Comet Tube Amp EA32-RVT  
 
Help on a Epiphone Comet Tube Amp EA32-RVT...  
I just got this old non-functioning tube amp.... So I replaced misc. browned caps with correct value replacements, the 4 filter capacitors, and the 2 power tubes (EL-84's from Mojotone) and the preamp tubes (2 Sovtek  
 
6EU7's) and the ? tube(phase splitter? reverb?) with a new old stock tung-sol 12AU7 and the blown speaker with a mojotone 10" of the right (8) impedance. Well -- it fires up!  
 
BUT -- the tone is all trebly and thin and bitey -- hardy sounds the wound strings on my guitar at all. Any ideas?  
 
I was an EE major once upon a time -- so I can handle meters and a soldering iron, Just never worked on tube stuff before other than replacing tubes.  
 
Any help for a newbie? Thought this old amp might be a good one to learn on.  
 
Mike Gardner  
 
-- "Life is too short to play a crappy guitar" -- Rick Nielson of Cheap Trick  
 
 
  
11/22/1999 3:37 AM
Farrow
Mike, it could be lots of things. Epiphone, right? Look for leaky coupling caps between tube stages. There shouldn't be too many of them, and if there's a DC offset on the grid of a gain stage, then there goes the bias and the tone. I'd replace ALL the caps in the amp. Maybe not the tone control caps, but certainly all the electrolytics. Make sure the catode bypass cap for th output tubes is OK also. Many times they're not rated at a high enough voltage (though with EL84s a 25V should be fine.)  
 
Also, I would replace ALL the plate resistors with either new stock carbon comp or carbon film resistors to cut down on noise.  
 
My .02  
 
Farrow  
http://surf.to/pharaohamps  
http://www.skybolt6.com  
 
PS I think I might have a schem lying around. If you want it email me back.  
  
11/22/1999 7:21 AM
Dave Stork
I don't have a schematic for that amp. But outside of malfunctions in the tone control circuit, I'd say that bad coupling caps are a likely cause. As the caps aged, their capacitance may have decreased, and in extreme cases it could lead to the symptoms you describe.
 

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