It's been a while since I've worked on a system 7 game, but working with the typical repair work flows on Pin Wiki and the old Marvin3M site etc. I have a Black Knight that locked on and burnt 8 of the 16 coils in the game. The ONLY fuse that was blown however was the 10 Amp fuse under the left side of the playfield and appears to have taken the left Magna Save magnet with it.

CPU boots, (flashes zero and 2 dots) and goes blank with the door open. (holds at 9 if the door is closed) I can get the game to attract mode by powering off/on quickly, but the display values are all 6's, with the exception of the credit window showing 11 credits (coin door buttons and switches register) and playfield switches activate solenoids, but no diagnostics show up on the displays correctly, only variations of 6's.

The battery holder has some corrosion on it, only one terminal appears to be bad, Batteries are off the board, and no visible damage due to corrosion is evident.

Can't get the game to start a game from attract mode, and without the diagnostics, I can't seem to pinpoint where the faults are. I'd guess it's a switch matrix issue, but I haven't verified this yet with Leon's chip (I think I still have this in the toolbox somewhere) and LED.

I'd normally have expected a PIA to have crapped out to have locked on the 8 coils (firstand certainly to have seen a fuse blown before these coils got to the point where they were melted solid.. I mean they are BLACK. (owner left the game on over night)

Suggestions on where to start looking next?
Or do I just send the boards out for diagnostics and repair and save myself the hassle and time?