Hiya DickFoster.....yeah the headphones output works fine......the amp was also working when i used the output on the back straight into the pa....so i'm thinking that if it was muted then that would also apply to that circuit too...but thanks for that
Actually no. The only thing that mutes with the heaphones plugged in is the preamp to the power amp that drives the speakers. All the other outputs headphone output, effects out and direct out will still function with the headphones plugged in. That tells us that your problem is likely either with the preamp, power amp or one of the supply voltages dedicated soley to one of those circuits.
At least that piece of info eliminates a whole bunch of stuff in the front end of the amp, the DSPs, processor, etc. etc. etc.
It's all about finding out what works and what doesn't so you know where to start looking for the problem. In electronics they call this the half split method of troubleshooting. You start in the middle of the overall circuit to find out if the first or second half is good or bad then cut the known bad half into half again etc. until you eventually get the problem isolated down to your problem component.
Now that you know that the front half is good, ever who works on it need only look at the back half to find your problem.
The fact that it's a stereo amp and both channels are not working should make it just that much easier to find the trouble. Armed with a schematic and common test gear like a DVM and scope ever who your tech is should have little trouble finding your problem and getting it put right again.