volume loss

Just wondering if anybody has had the same issue with their SVT-4. Was playing through Power Amp A only for some time into a single cabinet. One day I turned the amp on and it was really quiet. Switched over to Power Amp B and it’s fine. I’ve checked the stereo/mono modes, tried running bi-amp...

I switched the output jack and the pickup output on the volume pot as mentioned in other threads, nothing in reverse, Tone pot causes volume drop on Mustang PJ - need help please , Wiring Issue and Pickup Suggestions for Mustang P/J Bass and Tone pot causes volume drop on Mustang PJ - need help...