Repairing a Nakamichi T-100 audio analyzer

[Ron]

Hi:

I have a Nakamichi T-100 audio analyzer that has a problem. After
being on for 10 minutes or so, the bar graph display goes nuts- jumping
randomly, sometimes both channels, sometimes only one channel. After a
while, the bars "peg out" at maximum value and the very far right bars
are the only ones that remain lighted, even with no input.

Has anyone seen this problem? I have searched at no avail for a
schematic or service manual. My repair bench is piling up with tape
decks to repair as this T-100 is my main test instrument. It has been
my faithful test bench companion up until now. Help!