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High pitch squeal....


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2/6/2004 7:17 PM
Aris
High pitch squeal....
New homebrew Fender 6G6 Blonde Bassman normal channel only...GZ34 rectifier, 2x6L6, 2x12AX7. Works fine and sounds great, except for the following:  
 
1) When I flip the standby switch off after playing, I get a high pitch squeal for a split second.  
 
2)Also, the Presence knob doesn't do much except at the last 10% or so of its travel.  
 
I've swapped the OT primary leads to the 6L6 sockets, and nothing is different.  
 
Any ideas?  
 
Thanks for your help.
 
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2/7/2004 1:16 PM
Matt H

the high pitched squeal after playing is probably a cap discharging... most likely a filter cap.  
 
the presence knob- doublecheck your resistor values, check the pot value. it's possible you have a resistor that's labelled one thing but is actually another.
 
2/7/2004 4:00 PM
Aris Corkos

Is there anything I can do about the squeal? It doesn't seem to do it all the time, but it is pretty annoying...
 
2/7/2004 5:24 PM
Aris Corkos

The JTM45 schematic from the JTM45 Yahoo discussion group shows a .047uF cap between the standby switch and ground...would something like this help?
 
2/7/2004 10:01 PM
Matt H

that cap usually just kills the "pop" some amps have coming out of standby... but heck, it's worth trying it.
 

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