2001 Peavey Minx 110 - low output

[acorkos]

This Minx 110 bass amp has some problems...ultimately, it's suffering with low volume. The treble pot was subtley cracked, non-functional and measuring open. The 100uF filter cap on the PCB had a cracked contact. The volume improved slightly when I replaced/repaired the above issues, but the volume still is very low.

All the voltages and resistor values seem to check out, and all the components seem to be connected properly. The only unusual thing i found was a static noise when i touched/rubbed the connections of C102, R107 and leg 3 of U100 with a wood stick. I replaced C102 and U100, but no change.

U102...the opamp on a socket....leg 5 has -15.9V on it (pin 4 and pin 7 on this one are connected to the low voltage rails). When i removed the opamp, pin 5 on the socket had no voltage on it...this made me think the opamp was bad. i swapped in a new one, with the same readings.

The preamp signal into another amp is strong, and the guitar cable straight into the effects return has a weak signal...this power amp signal is weak through headphones, too.

Additionally, I cleaned the effects loop jacks and jumpered them with an instrument cable...no change. Connecting an extension speaker doesn't change anything, either.

I'd appreciate any suggestions on where to look next. Thanks!

[Enzo]

U102 is not an op amp, it is an OTA. PIn 5 is a control input. Did you replasce it with the SAME type? WHat happens if you just leave U102 out of the amp? I suggested that over in the PV forum. I won't duplicate here what I said there.