Yamaha PSS-680 No sound

by Iain
(Toronto, Canada)

Any advice on how I could troubleshoot this keyboard would be greatly appreciated.

Background:
I recently pulled my old Yamaha PSS-680 out of storage and dusted it off. I could not find the original power adaptor, but ended up trying a generic power adaptor with a variable setting for the voltage (3-12V).

Initial Conditions:
I set the generic adaptor to both 9V and 12V (ampage is 800mA), plugged it in and voila! I had sound (albeit unbalanced). The left speaker had a very low volume, the right speaker was audible but not as loud as I believe it should be.

Experimentation:
I found that a few of the digital synthesizer settings were just plain odd, and cranked up the total level (setting #8). This improved the overall volume, but it was still unbalanced.

The last person I am aware that played with my keyboard was my younger sister. It is possible that she played around with the settings.

Current Conditions:
A week later, there is absolutely no sound coming from the speakers. If I place my ear right up to the right speaker I think I can hear a faint sound. But a rapid degradation nonetheless.

I have checked the power adaptor (to confirm the voltage is within range), the digital synth settings in case someone else (my kids!) has played around with the various settings themselves.

Again, any help is appreciated.

Cheers,
Iain