Vintage Synth Repair

I just started experiencing this problem on my EX800:
After being on for anywhere between 1/2 an hour to 1 hour, the 
left(mono) output 
cacks out. There is almost no output and what is there is distorted. 
When I wiggle the 
cord at the jack or pull it out and re-insert it, it makes no 
difference. No crackle or 
anything. If I insert into the right output, it's fine. I did kind of 
trip on the cord a little 
just before it started happening, so I thought maybe I cracked a 
solder point, but with 
that senario, I would have expected intermittent output when wiggling 
the connection.
I'll check for a solder crack anyway, but I'm wondering what else it 
might be, if it's 
not that. The unit was also in a fire about 5 years ago. Any wise 
thoughts on this?
  Thanks,
             Shayne