GR-20 one sided headphone output - with no other outputs used

[davrosandthedarleks]

Dear Formum,
my GR-20 is only producing sound on the right headphone output.
Has anyone any experience or solutions?

I've had a quick look under the hood and there are some switched contacts on the outputs to change between headphones, left and right out and just mono out (3 sockets doing 1 of 3 jobs).
The previous owner said he only used mono out with his amp.

I will attempt to trace circuits and see if the main output is down or if its the digital output before that chip  has died, presumably there will be a single chip providing both final amplified stages to power headphones and the regular line outs.

Otherwise the unit plays fine and I can hear all 6 strings.

[davrosandthedarleks]

Managed to open the case, lots of screws and pay attention to where the different types go.
Flipped over the input/output board and applied some contact cleaner. Put a 1/4" jack in and out 10 times and now seems all fine. Just lack of use I guess. 

[gumbo]

Managed to open the case, lots of screws and pay attention to where the different types go.
Flipped over the input/output board and applied some contact cleaner. Put a 1/4" jack in and out 10 times and now seems all fine. Just lack of use I guess. 

...parts of my body act like that ...