I miss my Mega ST2. The motherboard on mine looked like the one you picked up for a spare. Where the RAM chips are is an outline of where more chips could go. I soldered in sockets on all of mine and added more RAM and turned mine into a Mega ST4. I never had a color monitor for it. I got the monochrome monitor as I used mine for Desktop Publishing with PageStream.
Thank you. I am glad you appreciate it. And you are right. There are not so many repair videos online of the Atari STs. Let's hope this one will be useful for someone.
Lot of work for such old computer :-) But if you can get the megabit D-ram for low cost, why not upgrade the Atari to 4 MB? I believe it can be done with the piggybank method ;-)