Good Morning,

This is my first post! having an issue with Fender BXR60 Bass amp. There is a hi-pitched "tone" (low in volume, more like a non directional vibration) when there is nothing connected to amp and volume is at zero. When I connect my scope to the speaker, I get a very high frequency waveform that is about 10millivolts @ 0 volume and .4 volts @ full volume. I traced back in previous stages and do not see it, I think the problem is in the last stage. Can anybody point into a troubleshooting direction? I have replaced the power supply filter caps. Thank you very much in advance and I have posted the schematics. David