According to the service manual Q506 is driving the sled motor and the pickup linear servos. You may have some machanical problem in the pickup itself, this may cause the IC to overheat. you can (VERY GENTLY!) lift the plastic cover of the pickup and look for anything that might limit the lens movement. If its not something very obvious, I would return the plastic cap and try to check capacitors C506 ; C503 (1000uF 16V) to see if there is any visible deformation (infalted or leaky). If you have a scope, check dc volatge on these caps as stephensank suggested. If you don't, I would offer to replace them. One important check is to see if the IC runs hot while NOT playing a cd.
If you need a service manual for this model you can get it at HIFI engine.
Let us know what you found.
Frankly, though, if this player has the MASH dac that it's listed as having, it's not worth putting much effort into. Those dacs are quite mediocre at best, no matter what you do with them.