I would check the power at the boardset for sure, Could also be a bad ram or more.. with my si i had 2 bad rams..
I found the bad ones by using a test rom.
I dont know how far racine is from the il border, im south of beloit... so if you want to make the drive lmk and i will try to find my test rom .. i have a tube of nos ram chips courtesy of "scam controls", so i would donate a few ram chips to the cause if thats what your issue is.
I can borrow you the test rom and give you a couple ram chips, or if you just want to hang one some day and ty to fix it here( we can test in my machine) lmk
edit, wait, havent we already met or am i thinking of somebody else?