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Unread 05-24-2010, 10:48 AM   #16 (permalink)
Joey Voltage
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Join Date: Dec 2009
Location: Brighton, MA
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Re: Fender bassman 135 fix...

Quote:
Originally Posted by Wilder Amplification View Post
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.
That is if you are absolutely lucky! In my experience most the damage has been done by the time that screen resistor pops. and is the last place I would look for protection or insurance



Quote:
Originally Posted by Wilder Amplification View Post
Two 100 ohm resistors off the heater winding to create a false center tap is also common practice as well.
what he has is a humdinger he wants to measure the pot to see if 100r will work fine. remember Jon you don't want to go crazy with the value here. I suppose I could just look at the scheme and tell him though, but memory tells me it is 100r or so, so the two 100rs are just within the limit. plus I already said this crap already.
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