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Unread 05-24-2010, 01:19 AM   #9 (permalink)
Wilder Amplification
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Re: Fender bassman 135 fix...

I second the Major's assessments. 470 ohm 2 watt resistors are typically what most Fenders used stock. You don't want to overrate them too much. The fact that one got taken out when the valve shorted is a good thing as once the screen resistor goes it basically pushes that valve into cutoff and turns it off. As such, the screen resistor acted as a fuse. Overrating it will make it harder to blow in the event of a catastrophic failure where it can cause much more damage, such as taking out an OT or possibly even a PT.

Two 100 ohm resistors off the heater winding to create a false center tap is also common practice as well.

And 100uFs are fine for the bias filters as well.
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