Help tracking down SE/30 board issue

[jonschwenn]

^^ video of current state

This was a clean SE/30 I picked up recently. There was no visible damage from the capacitors leaking. It booted with SimasiMac symptoms. I had the board re-capped, and purchased new memory and a BMOW ROM. Since then, it boots to what is seen in the video link. I reseated the RAM and ROM multiple times and tried to clean up areas with detoxit. When that didn't work, I had the (4) video multiplexers on row 8 replaced which did not fix the issue.

I've reached the limit of my own abilities and was hoping someone would give me pointers on what to look at next to track this down.

 

[ymk]

It looks like one of the lower video address lines is broken.

 

[jonschwenn]

I'm assuming it's somewhere in here - https://github.com/mishimasensei/ma... SE_30 Schematic 05 of 09 Video Interface.pdf

Can you point me out to which pins to try to track down? I'm just looking for some hunches to use as educated guesses as places to start

 

[ymk]

Check the A(x) inputs to the 74F253s at the IC pins.