I really tried to google the hell out of this issue. I have the service manual and I have read nearly every thread on this website about it. I understand that the SM says this is a "Bad ESP Error" and says problem is on the digital board and to replace the entire thing. I am hoping to narrow it down a little more than that.
I noticed a little more nuance in my symptoms, shown in this video:
The screen seems to flicker every 2 to 3 seconds after initially turning it on. Can this suggest a power issue?
I took the back cover off and found the following: (1) there may be a single pin missing from the data ribbon jack on the back of the disk drive. Not sure if it's meant to be like this. And (2) there are some suspicious looking jumper wires and frankenstein ICs soldered to the main board. See photos:
Things I've tried already:
1. spraying inside the disk drive with canned air.
2. re-seating everything that can be reseated (ribbons, chips, simms).
1. check PS voltages
2. make/order new OS disk (It was given to me, someone made it recently and I don't think this is the issue but may give it a shot)
If any of these symptoms or observations mean anything to someone I would appreciate some help. Thanks in advance.