Color issues

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Incorrect colors can have various causes. In order of probability: bad JAMMA contacts or wiring, split SCART cable, monitor failure, damaged video DAC, bad palette RAM, cut traces between GPU chips (check P bus)...

The color test screen in the system ROM menu can help diagnose problems (burned DAC resistors...).

Example screenshots are from Blue's Journey.

To do: System ROM test mode monitor test screenshots.

One missing color

Two missing colors

Three missing colors

Enjoy the sound :)

Shorted color lines

This can give very weird colors, since outputs will "fight" with varying strengths.

Missing sync

Rolling or distorted display, most probably a bad contact. If not, check SYNC.