In for repair was a Spectral Vs. Generation (SVG) cartridge for the Poly Game Master platform by IGS. It was booting up to a garbled screen.
SVG was a late release for the PGM platform, and it incorporates strong anti-piracy measures that IGS didn’t have in their earlier games. The cart has an ARM CPU with an embedded ROM that both decrypts encrypted assets and processes some of the logic for the game. The game has yet to be patched to operate without the ARM CPU, and the embedded ARM ROM hasn’t been fully dumped yet with this game. If the ARM CPU fails, that’s pretty much a project killer.
The owner of this cart also sent along a fully functional second SVG cart, and through cross-testing, I confirmed that the CHAR board of the faulty cart is fine while the CPU board is the culprit. I dumped the three EPROMs from the CPU board and while the dumps matched MAME, the good cart wouldn’t boot with the “V200 U30” EPROM installed from the faulty cart, so I programmed and installed a replacement 27C4096 EPROM for that part.
This still didn’t get the faulty cart booting so I moved on to reflowing the ARM CPU and confirming that the ARM was receiving a clock signal from the onboard crystal at U35. The cart still froze at bootup so I reached out for help on the Arcade Projects forums. On there, Fluffy helpfully suggested installing the three GAL chips from the functioning board into the faulty board – a dumb oversight on my part. 😀
Installing the GALs from the working cart got the faulty cart booting to an EXTERNAL RAM TEST ERROR screen.
Replacing the SRAM chip located at U38 resolved this error and now a new error appeared – SHARE RAM 1 TETS (sic) ERROR.
I replaced both the SRAM chips located at U37 and U38. This resolved that error and now the cart was booting up successfully!
I still needed replacement GALs though, and the GALs for this game hadn’t yet been dumped. I reached out to Apocalypse and he graciously offered to dump the GALs for me. I shipped him the carts, he dumped the GALs and the PLD files are now available at the PLD Archive.
Now that the original good GALs were installed back in the working cart, the final step was to program fresh GALs with Apocalypse’s PLD files and swap them into the faulty cart. The faulty cart booted up fine and passed a four hour burn in test. Repair complete!
