I’d worked on a few prior – but they were for friends and I wasn’t sure I wanted to start taking them for repairs.

Board #4 – In for repair

Received Condition

This one started as they all do – cleaning chip legs and Deoxit. Helps make sure there are no contact issues.

The board powered on and booted, allowing a few minutes of play before entering a repeating reset cycle. The problem was not heat-related, though it appeared that way at first. During startup diagnostics, the board consistently passed the ROM check and occasionally passed the RAM check, but always reset before completing the non-volatile memory check. The boot loop went back / forth between these 2 screens.

Repairs

• Identified and replaced a faulty ROM chip (ROM 306) as the root cause of the repeating reset cycle. This chip was borderline-failing, making it difficult to detect. It passed the built in ROM check and passed on the bench in my tester.
• Replaced a logic chip (LS245) as part of the diagnostic process; this was ruled out as the cause of the fault.
• Used a pull-up resistor network as a diagnostic tool to isolate the fault to the ROM area of the board.
• Replaced two non-compatible 9101 RAM chips found in the video RAM section. These were not related to the reset problem but were causing graphics issues.
• Investigated the clipped image on the right side of the screen. The cause was traced to RAM chips in the color graphics area that were too slow for the specification required. These were replaced with the correct-speed 93422 RAM chips, resolving the graphics problem.

Final Outcome

The repeating reset cycle has been resolved. The board now progresses correctly through all startup checks. Both the faulty ROM chip and the unrelated video RAM chips have been replaced, leaving the board in improved overall condition.

At first, I thought my LCD wasn’t a fan of the video signal – however – after connecting to 2 CRTs – it was the game board. Took a while to find the source of the clipping on the right side (no blue border). It was 2 more 9101 RAM. Typically they can substitute – but not on this boardset. 93422 RAM is much faster. Replacing these also corrected the issue.

Board Works!