How bose companion 3 speaker system volume problem can be fixed?

SOURCE: control pod on bose companion 3

try to check the circuit board with an expert

SOURCE: bose companion speaker stopped working!?

What happened to you is probably mere coincidence with your cousin's use of the headphones and this is throwing you off. I own the Bose Companions also and they stopped working as well. However, I traced the problem to the "wall wart" power supply. Not sure why but Bose is now using an interchangable plug on them. If you look at the power supply you will see a "PUSH" button. If you depress it the plug can slide out. When it is slid back in and locked in place the connection between the plug plate and the power supply is not a good one. Try fiddling with it. But even if the connection is not the culprit, something in the power supply is. I swapped another power supply with the same connector and spec's ( amps must be the same ) from another item and the speakers worked perfectly.

SOURCE: Does the Bose companion 3 have an internal fuse?

Yes. The companion 3 system can be repaired for $75. Call Bose at 800-367-4008. They will also give you a new 1 year warranty.

SOURCE: Control Pod for Bose Companion 5 speaker system

I had the same problem right out of the gate, the volume dial on my control pod for my Companion 5 wasn't working, however, the touch pad and LED worked. I called Bose customer service and was instructed to:

First, unplug the power directly at the back of the woofer while the unit was on;

Next, I was instructed to unplug the control pod, visually inspect for any damage/defect;

Finally, re-seat the control pod on the back of the woofer and then lastly plug the power cable back into the woofer.

It worked like a charm. I hope this is helpful!

SOURCE: Bose Companion 3 series II speakers aren't producing sound (imac)

from what I've read, the imac has a 3.5mm (.138) jack while the Bose jack is 1/8 (.125). very small difference in size (.013), but enough to cause problems.