Scanner SK, that diagram must be a Pro-106 not a PSR 500. Speaker on top on a PSR 500, bottom (as your diagram) on Pro 106.
Good catch! I removed the diagram to prevent confusion.
The two pictures however are of my PSR-500 and show the effort that may be required to fix the ribbon. If it were the ribbon, I believe a person could simply press down lightly on it or move it gently to make the display alternate between working and not working.
I was thinking down the line that maybe too much voltage or AC is getting into the scanner skewing the frequency of the clocking crystal or something down that line. It seems almost as if the display CPU is locking up.
In the Service Manual for the PRO-106 (nearly identical to the PSR-500) I just noticed that it mentions doing an EEPROM check to verify the display IC307 is working properly. This procedure clears all stored information from working memory so a person needs to save everything to their computer or into a V-folder before proceeding with this procedure. The procedure is done by pressing "0" immediately after turning on the scanner and then press "5" and then "Enter".
Shawn