Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: michaelmeader on May 26, 2018, 07:11:08 pm
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Hi folks, i recently got a 1972 fender super six reverb. It had the bias balance set up. I changed it over to the blackface style as per dougs pictures. My tubes bias within spec, but i was a little unclear about one particular white wire. (Sorry i didnt take pictures) this white wire originally was hooked up to the back single lug of the pot along with a cap, and i believe a 3.3k resistor that went to the bias supply. THE OTHER END of this white wire travelled to the board and connected to a 2.2m resistor, the trem circuit i do believe.
I removed everything that wasnt shown on dougs blackface picture, but the picture didnt say or show what to do with this white wire that ends at the 2.2m resistor. At first i left it disconnected, amp worked fine, trem and reverb also worked fine. Then after a little researching, i looked at a twin reverb ab763 layout, and saw where this white wire is hooked up to the bias supply, without all the extra stuff i had removed. So i hooked it up there, approx -70volts.
Did i do this correctly?
Is the white wire from the bias supply to the 2.2m resistor even needed? It worked without it.
If i leave it hooked up, is -70 volts an appropriate voltage needed?
Any guideance would be appreciated, thankyou, mike
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The white wire to the 2.2M ensures the trem oscillator will be off when switched off. But, it also acts like a quick "Kick start" when you switch the trem on. The trem will still start up without that connection but it may be slow, especially as the tube ages. I would leave it connected and enjoy a fast starting trem.
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Ok, thanks