Vintage Synth Repair

the short of it:  a SC Prophet 5 3.3 with MIDI with LED's/front panel
display that flickers intermittently (especially after receiving MIDI
info for a while).  the visual flicker correlates with an audio
"flicker" (imagine rapid, digital-sounding oscillations modulating the
VCA).  anybody had this problem before?  is my car about to overheat?
 generally it lasts through some preset changes, power off/back on,
different outlets...then finally decides to shape up.  I'd sure like
to meet some empathizers.  thanks-st nich