I would go through the circuit systematically.
Check for broken wires around the circuit. It happens and you will feel like an idiot if you skip to the next bit first (ask me how I know...)
Make sure the board didnt shift in the case, which may cause things to short that were previously good. (this one is good and humbling)
Just swap the chips to see if its the opamp. if you have no spare opamps radio-shack sells the really cheap opamps that are great for testing circuits. I think its TL081 TL082 single and double respectively (dont quote me unless Im right)
After that things get harder. I would look for cold or dry solder joints, and perhaps give everything a once or twice over with the soldering iron.
Edited by nikongod - 8/5/10 at 8:43pm
