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previous: Albert Kreuzer Prosonic with frying noise -- 10/16/2003 2:43 PM View Thread

Same noise, plus hum and oscillations - HELP!

11/5/2003 8:58 PM
Albert Kreuzer
Same noise, plus hum and oscillations - HELP!
THE RETURN OF THE SON OF THE HISS AND THE HUM... 8-(  
 
The amp was fine for a couple of days - now it's back on the bench.  
Not only that the frying noise is back (both channels, worse than before), it also has an annoying hum (gain channel only). When I turn up both gain pots, the amp starts to oscillate at 200-300Hz, frequency changes with different gain settings. Also the master volume setting slightly affects oscillation frequency.  
Hum gets louder with gain 2.  
No oscillations when I switch to clean. All tone controls down: oscillations stay on the scope (pin 6 of V1), but no noise at the output.  
 
Anybody who can point me in the right direction? (BTW: I'm not "a real tech" but "a real professional musician" who gave up his EE studies for music)  
 
http://www.ampwares.com/ffg/schem/prosonic_schem.jpg  
 
Thanks for your time  
Albert

 
Replies:
Dai Hirokawa [QUOTE]it also has an annoying hum ... -- 11/6/2003 3:28 AM