SOLVED Sega saturn - BIOS pinout

I've done many BIOS replacements on SEGA saturn in the past with great success. Recently, I was asked to install a region free BIOS into a white Japanese Sega saturn (HST-3220 / Model 2). The systems belongs to me so no customer console was lost in the process.

To my horror, Sega went CRAZY with the amount of goop under the BIOS. Rather than the typical 3-6 dots, they smeared almost the entire PCB! With enough time, and patience, I managed to remove the original BIOS but some traces were broken.

I managed to figure them out, and fix them EXCEPT for 1. Pin 1 on the BIOS, pin 3 on the replacement BIOS is A17. This typically (according to schematics) connects to IC28. IC28->IC30 are bus transceivers that the BIOS pins connect to. But with this system, Sega replaced those 3 off the shelf 74LSxxx parts with 1 custom SEGA IC!!!

Now for the life of me, I can't figure out where it goes on this IC because the trace for that pin and corresponding VIA are located under the goop. Worst yet, even if I clean the goop (good luck to me with that) the VIA's are located under this custom IC that is on the other side of the PCB!! ARGGGG..

WHY SEGA.. WHY... SO MUCH GOOP!?

Anyone got schematics for this thing?? Anyone can tell me what this BIOS pin connects to?

Thanks.

 

x

 

The board is 171-7128C. I ended removing the BIOS (AGAIN) and spent an hour scrapping away the goop. Under it was not 1 hidden via, but 5! Discovered the correct broken one, wired it up, and surprise surprise .. the Saturn now boots perfectly!

Super happy.

But I still blame Sega for using excessive amount of goop to hold the BIOS down.. oh why!?