In amongst all the chaos of testing chips on various H4's... #3 seemingly died for no reason which I just investigated.
All the clocks were present but I never saw /AS going low ( or if it did, I did not detect it on my scope). Probing around I saw RESET was switching, but HALT was stuck low all the time. I removed the CPU and HALT started to function correctly again. I noticed a bent pin on the CPU, always one of the corner ones, honestly I seriously hate PLCC packages! But nope, still no boot.
I took the ROM out to make sure it did actually have TOS104 in it.. and after fighting with a iffy PLCC adapter for my programmer, I found them verified TOS was in the lower bank. I also found the ROM also had a bent pin on the corner, and I mention I hate PLCC packages ? But nope, still no boot.
I swapped out the CPU,MMU,GLUE with known working ones but still no joy...But then I noticed something....

- IMG_5049.JPG (277.83 KiB) Viewed 6563 times
Let's see who can see what is wrong, I was frankly amazed by this in more ways than one... I guess us season builders will spot it right off...
Needless to say this board is now booting again now
