MV-6 intermittent calendar error

My 6-slot Neo Geo had been in storage for years. Before powering it on, I resoldered the PSU and inspected the pcb. Unfortunately the battery had leaked so I removed it and cleaned the area with vinegar. The damage had been done, see the attached pics of the board.

When I powered on the cabinet it got stuck at the green screen, meaning a calendar error. Since I had a 32kHz crystal I replaced it to be sure. When I powered it up without screws joining the pcbs I got the crosshatch! Fully content I put back the screws and there is was: the green screen

Later I unscrewed it again to measure the clock IC and damn, all voltages were fine and everything worked. I'm a bit stuck here, when I unscrew the system everything works so I guess it must a bad trace somewhere. I also struggle to find out where the traces go.

Does anyone have the schematic of the 6-slot calendar circuit, or any other tips to help me fix this?

Use your meter to check continuity between the vias on the traces/areas circled in red. It's going to be a pain, and take awhile but it's really your only option. You'll also need to put in a coin cell battery, or a new rechargeable battery. (if you put in a coin cell battery/battery holder, you'll have to remove that 470 ohm resistor on the boad. just snip both ends. This disables the charging circuit.) If I remember correctly, you'll get certain calendar errors when there's no battery present.

Also, see all the resistors, diodes, and transistors above the battery area? Check them too. I've had a few times where the legs to the resistors corrode off the body of the component, but still look like they're attached. Check each one individually.

As for the traces, if there's no continuity between any, you'll have to patch them with some very thing gauge wire.

Good luck

RetroTechRewind said:

Use your meter to check continuity between the vias on the traces/areas circled in red. It's going to be a pain, and take awhile but it's really your only option. You'll also need to put in a coin cell battery, or a new rechargeable battery. (if you put in a coin cell battery/battery holder, you'll have to remove that 470 ohm resistor on the boad. just snip both ends. This disables the charging circuit.) If I remember correctly, you'll get certain calendar errors when there's no battery present.

Also, see all the resistors, diodes, and transistors above the battery area? Check them too. I've had a few times where the legs to the resistors corrode off the body of the component, but still look like they're attached. Check each one individually.

As for the traces, if there's no continuity between any, you'll have to patch them with some very thing gauge wire.

Good luck

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Thank you for the input. Is there a schematic available or is this something I would have to reverse engineer?

The resistors, diodes and traces appeared to be good as far as I could reverse engineer.

For now the calendar issue seems to be fixed after cleaning, resoldering, and putting in a new battery.

Next up is fixing the whining power supply and 3 malfuntionings slots.