Slobrain 8/3/2016 7:53 PM
Fender Frontman 25R wont channel switch, need schematic
Hey Folks,

I got a Fender Frontman 25r combo amp that was my nephews. Its stuck in the distortion mode, I tried using the footswitch and see the red led going on and off on the amp but even though the led goes on and off it stays in distortion mode. I never worked on a frontman and don't have any schematics to this amp. Does anyone have an idea what might cause the issue? its not the switching jack,. Its in the electronics where its stuck and without a schematic I can't tell what is used to channel switch this amp.

Thanks
 
Enzo 8/3/2016 8:02 PM
Nick has three files Frontman 25R on his site, here is one.

http://bmamps.com/Schematics/fender/..._schematic.pdf

If the LED goes off and on, then teh footswitch circuit is working. There are two JFETs that do the actual switching, and perhaps one is bad.
 
Slobrain 8/3/2016 11:13 PM
Thanks for the schematic Enzo, yes looks like Q1 was bad... Now to see where I can find a local place that sells J111 jfet. Seems this is a more common problem with these 25R amps. I have an old stash of transistors but I don't think I have any jfets...

Too bad Rat shack doesn't carry these any more...

Thanks
 
Brbluetele 10/7/2017 4:34 PM
Can this j111 jfet be installed backward?
 
Jazz P Bass 10/7/2017 10:36 PM
No, they cannot.
Well, physically I guess they can.
But not if you want them to function.

Pin 1: Drain
Pin 2: Source
Pin 3: Gate

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