AMPS troubleshooting

[jerry8jb]

Hi guys, maybe I'm not in the right forum, please redirect me if required.

Behringher B300 active speaker problem:
-started with noise when "playing with the input jack.
- now I have a background hum/noise when selected on "line". No noise when on "MIC". There is no noise when the speaker is on with nothing plugged in it.
- I try changing cable. No effect so I eliminated the cables issue.

- I opened the amp, inspected see nothing special.
Try to find troubleshoot guide on the net but nothing.

Can someone give me some "simple /basic" troubleshoot I can do??
I don't have a lot of experience with amps but ready to learn. Where should I start?

Thanks.

Jerry

[johan]

It seems like the inside of the input jack might have worn out. Had this with my own old solid state Fender Power Chorus.

Does it give a steady measurement with the multimeter?

[johan]

I looked up the Behringher B300 active speaker because I realised that it's not at all a guitar amp. It surely isn't constructed to be used with a guitar, but it could work, that is, give some sound. But it won't sound good, I fear

J