Fender Frontman FM25-R BASS issue

[dpve1@aol.com]

Hi,
Now that I have both channels working again, on to the BASS issue.
The amp is incredibly bassy, and I was thinking it was the speaker.
Now that I have a second amp to test with , I hooked up the FM
to the other amp's speaker and it was bassy, so I think I ruled out the speaker.

Does not seem there is any adjustment possible with bass knob on the front
panel, always seems like bass is turned all the way up regardless of
position of the BASS knob.

Is there some basic troubleshooting?
Where to start?

I have the schematics for the amp available.

TIA

[pecorporation]

A quick test might be to loosen the nut that secures the bass pot to the front panel and see if shifting the pot around in its hole while playing to see if the bass response changes. This may indicate failed solder on the pot or possibly a defective pot itself.

What did you repair on the amp first time in?

[dpve1@aol.com]

I replaced Q1, no where near R31.

[pecorporation]

If the bass worked before you did the repair, the problem may lie in the bass pot, it's solder connections or possibly an errant solder bridge somewhere which happened during the first repair. With the amp unplugged, clip an ohm meter lead to the pot side of R33 and the other lead the pot side of R34 and check if the resistance value changes when you turn the pot. This will let you know if the pot is variable and it's solder connections still good. Then use the ohm meter to see if the ground pin of the pot is actually connected (zero ohms) to ground.