You can run the artificial center tap resistors from the indicator lamp terminals to a solder lug under the closest PT bolt. Example: http://el34world.com/Hoffman/Princeton_ ... _Build.htm
(This is assuming your amp is still using a standard Fender lamp.)
Blown screen resistors and more
Moderators: pompeiisneaks, Colossal
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- Posts: 131
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Re: Blown screen resistors and more
Ah, that's the thing. It's currently using a 220v pilot lamp.drew wrote:You can run the artificial center tap resistors from the indicator lamp terminals to a solder lug under the closest PT bolt. Example: http://el34world.com/Hoffman/Princeton_ ... _Build.htm
(This is assuming your amp is still using a standard Fender lamp.)
Re: Blown screen resistors and more
This should not share the audio circuit ground. The ground point can be at any convenient spot on the chassis.titser_marco wrote: 3) My heater taps do not have a center tap, so my tech advised me to ground one of the heater taps. Currently, it's grounded to the chassis. Should I use the 2x100ohm grounding resistors on heater taps, and then ground it to where the PT ground is attached?
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- Posts: 131
- Joined: Tue Mar 13, 2007 3:08 pm
Re: Blown screen resistors and more
So I put in the heater tap resistors (150ohm, 100ohms was out of stock) and the hum was minimized.
Now I noticed that the NFB resistor was disconnected so I resoldered that. Lo and behold the hum was GREATLY minimized. Now, the amp only has that his at max preamp and master volume and a very low level 60hz hum at zero preamp volume but max master volume. So I guess my question is: is it possible to have a 100w guitar amp with no NFB to function without hum?
Another thing: I'm finding it strange that the 60hz hum is loudest when the preamp volume pot is at the middle. Could this be a pot issue rather than a grounding issue?
Thanks!
Now I noticed that the NFB resistor was disconnected so I resoldered that. Lo and behold the hum was GREATLY minimized. Now, the amp only has that his at max preamp and master volume and a very low level 60hz hum at zero preamp volume but max master volume. So I guess my question is: is it possible to have a 100w guitar amp with no NFB to function without hum?
Another thing: I'm finding it strange that the 60hz hum is loudest when the preamp volume pot is at the middle. Could this be a pot issue rather than a grounding issue?
Thanks!