Yamaha psr8000 mic problems

by Simon
(France)

Has anyone else seen this problem?

I have owned the PSR 8000 for a few years now, never been gigged, but my favorite toy and relaxation method. Today, I switched on and the mic input doesn't appear to be going through the internal amp! I get the signal light working when there is input, and the "over" light comes on if I crank up the input level, so the keyboard is actually receiving the input. (I tried a different mic, but still the same problem) Just no output to the internal amp, and no vocal harmony obviously. The rest of the keyboard is working 100% OK. Please can somebody point me in the right direction

Thanks

Simon