Okay here is what happened. After I installed the socket for the NVRam. I made a mistake and I thought I would reflow solder at the connections and change out the cap at C31, while the board was out and convenient to do all at once. The cap install was no problem, however when I reflowed solder at the interconnect ribbon cable between the CPU board and the Powerdriver board, I caused a solder bridge to ground at one of the contacts.
This cause “the thing” to pop in and out continuously. And it blew a 5a fuse at F111 on the Power Driver board (this was causing the game to reset over and over)
The dead DMD was caused by the ribbon cable at J60 (top right thin ribbon cable) on the Dot Matrix card. I had accidentally reversed it a week prior (I had tested another DMD in the machine a week before and connected the ribbon cable wrong then, and did not fire up the machine before pulling the CPU board for the NVRAM install, so I never noticed the DMD was out before I even began the install.)
The installation of the NVRAM socket went flawlessly and looked like a pro job (I have installed many sockets); which was what was so confusing. But that flawless socket install was marred by several rookie mistakes: flipped ribbon cable to DMD, solder bridge at connector, not noticing the blown fuse afterwards, not doing the CPU board in stages.
Going ahead and doing a “quick reflow” of solder “while the board is out and convenient” is a mistake.
I should have:
-removed ram… installed socket…installed NVRAM and reinstalled board in machine and tested
-then reflowed solder at a connector reinstalled board in machine and tested
-then reflowed solder at next connector reinstalled board in machine and tested… and so on.
-replaced the cap reinstalled board in machine and tested.
Regard the anypin NVRAM from lockwhenlit.com works great, and was worth the effort. However if you are inexperience with chip removal and socket install I do suggest having an experienced tech doing it. If your game has its own socket that holds your ram, you will be okay installing it yourself.