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Correct Bias for 1964 Deluxe Reverb?! Thanks!


 
11/13/1999 4:17 AM
rb
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Correct Bias for 1964 Deluxe Reverb?! Thanks!
Can someone please tell me the correct bias for my 1964 Fender Deluxe Reverb Amp? I am running NOS Sylvania 6V6GTs. The Amp Probe guide said to bias 6V6s from 22-28 mV. Thanks! Rb
 
11/13/1999 6:46 PM
Rob W.
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RB-  
 
Try to aim for about 30mA per tube. But make sure the plate voltage does not go over 425V!!!! You will FRY your tubes if you run them too hot in any Deluxe.  
 
Good Luck!  
Rob W.
 
11/13/1999 11:35 PM
John Stokes
Let a fellow 64 Deluxe Reverb owner help you. The bias probe guidelines are about right. I usually set the 6V6s in a DR between 25 and 30 ma per tube at idle. Since you say you're running NOS 6V6s, don't worry about the plate voltages, they'll be fine. (Recall that Jim Kelly amps ran 6V6s at about 470 volts or so, and they lived!!). One notable "guru" advocates using idle current to intentionally sag the power supply. That is totally bogus.  
 
 
11/14/1999 12:46 AM
rb
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Thanks guys! Rb
 
11/15/1999 6:37 AM
Jim S.
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I believe the "guru" you are referring to is Gerald Weber. I agree with your assessment of his advice to run 6V6's at 30ma or even higher, to get the B+ voltage below 425VDC. Given good quality 6V6's, overheating them has GOT to be worse than pushing the plate voltage.
 
11/17/1999 9:19 AM
Dave Stork
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Hmmm.... I guess whoever suggested running at more plate current in order to sag the voltage, doesn't understand that what matters is plate dissipation, which is current times voltage!  
 
I love those "gurus." They're always good for a laugh.
 
11/19/1999 3:26 AM
liketubes
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rb,  
the correct bias depends on the plate voltage -not some magic number .. read Randy Aiken's article  
on this (his web site is www.aikenamplification)  
 
Randy's 'not greater than 70%' of max plate dissipation  
is right on -imo - since 6V6'ers are designed for  
a max of 14 watts in an class AB1 biased amp,  
that means your max idle current should be set to  
whatever yields not more than 9.8 watts -which  
is computed by multiplying your actual plate  
voltage times the bias current. For example, if you have  
425 vdc on the plates then a 23 milliamp bias would give you  
a 9.775 watt bias setting.
 
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