Biasing a bandmaster

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Biasing a bandmaster

Postby Beatle23_5 on Sun Mar 15, 2009 7:01 pm

OK, I have a 63 blonde bandmaster that needs to be biased...the tech in indy is so backed up he said it will be three weeks until I get my amp back...can't do it....I have shows to play.... Anyway I need a step by step rundown on how to bias this thing...I couldnt really find anything on google...Myself and my roomate are rather electronically designed....we both build pedals...stand alone fender reverb units...cap jobs...but have never attempted the bias....any help would be appreciated
'63 Blonde Bandmaster 6g7A
'68 Gibson Duo-Medalist
'71 AIMS Vt100
'05 Strat w/ '62 Reissue pickups and Stumac Birdseye maple Neck
'04 Orange Fender Cyclone
Home made handcarved SG---made by my roomate/bandmate....KILLS....

http://www.thevorticists.com ---if you like psychedelic type music, you should check it out
Beatle23_5
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Re: Biasing a bandmaster

Postby jcs on Mon Mar 16, 2009 9:33 pm

alex, i use a weber bias rite that shows plate volts and cathode current with the flip of a switch.

in the case of your bandmaster it is fixed bias with no bias pot, so you have to adjust the cathode current by changing out the bias resistor..

bigger resistor means less cathode current (cooler).

a smaller resistor means more cathode current (hotter).

and of course as you allow a bit more current to flow the plate volts will drop a bit (and vice versa).

there is much controversy over the several methods to adjust cathode current ,maybe others will post here.

one rule to remember is the tubes should never show ANY redplating in a darkened room,by this i mean the PLATES on the tubes should show no sign of a red stripe anywhere.
jcs
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