So after a few months hiatus from trying to repair this sucker, I decided to have another go this weekend.

So here is my Setup:

I have a Supergun which I have made a SI adaptor for (tested and works fine). I do not have any of the original roms and I am using a BRAZE multigame to help find any dead ram.
I have two L shape SI boards, one I got working quite some time ago, and it was a simple fix to find a replacement Xtal, and replace some LM 3900's to get the sound back. Done. The other Is being a pain in the butt!

What I have done so far:
The BRAZE multigame told me there was bad RAM at G8 which I socketed and replaced. Then it told me there was a bad RAM at G14, which I also replaced. Unfortunately the BRAZE multigame still keeps telling me there is bad RAM at G14, I then replaced H8 and H14 just to be sure...no change.

I have tested the board by removing the BRAZE and replacing the original 8080 CPU to see what the lines on the screen look like...they look perfect, just how they should, which is a good indicator that it isn't bad RAM anymore.

Yesterday I replace the following:
F14 - HD74157P
H14 - 74161N
and the two 8216's at B3 and D3

...No change whatsoever. I still get a bad RAM error at G14  :-(

Below you can see the board powered up using the standard SI test ROM.