Digitech RP200 Problems

[RickL]

This might not be the most appropriate place to ask this question, but what the heck...

I am trying to repair an RP200 that has some unusual symptoms. When using a mono output plug  only the wet signal is output. If I plug a stereo plug into the output both the left and right output signals buzz loudly with the guitar signal very faint in the background.

The headphone output works fine and if I plug either a stereo or mono plug into the headphone jack the mono output works well and plugging a stereo plug into the output again gives buzz in both left and right outputs. Also the two largish three-pin chips are getting quite hot. One is a 5 volt regulator, the other might be a power transistor to drive the headphones.

The guitar input and output jacks are switched stereo jacks and the headphone jack is a 1/8 inch unswitched jack.

I can obviously do a work-around to use the mono output by plugging a dummy plug into the headphone jack but I'd like to fix it properly. I know it's a longshot but does anyone have any idea of what might be causing this?