Repair Log: Taito G-Net arcade PCB

Status: Successfully Repaired on 1/31/2022

I’ve had a Taito G-Net board sitting in the repair queue for a few months, and I finally tackled it this weekend.

This board had an issue where Coin 1 was shorting to Ground, causing games to constantly reboot with a Coin Error message. Enabling DIP Switch 4 lets you access the Service Menu at least.

G-Net uses a Sony ZN-2 for the base board. I know @Hammy does a lot of work on this hardware, so I reached out to him early on. He told me that the 74LS253 TTL logic chips that handle control inputs fail frequently.

I traced Coin 1 from the JAMMA edge, through a few vias, resistors, and capacitors, and finally landed on Pin 3 of IC558.

Sure enough, when I tested this pin for continuity with ground, it beeped through on the multimeter. None of the other 74LS253 chips did for the same pin.

I carefully desoldered the failed 253 TTL, and swapped in a fresh one.

Now the Coin 1 input registers correctly. I played a full round of G Darius to test things out, then left it to soak test overnight.

Happily, everything still functions correctly one day later. Successful repair!