Look to see if the byte (or the previous two bytes) before the text string matches the count of the bytes in the string. If so, then look for that address.
Hi cruff. Yes, I've resoldered the socket of the DOC II and cleaned the socket with deoxit spray. PSU is recapped. All electrolytics on main board (other than some on the analog section) replaced. All caps on display board replaced. 20 pin ribbon cable to keyboard replaced. 20 pin headers on both sides replaced. Cable going to display board cleaned. Seems fine.I haven't gone back and reread the whole thread, but have you resoldered the DOC II chip's pins (or those of its socket)? Have you checked the caps in the power supply? Are any of those leaking? Is there noise on the power supply rails?