A lot of times when testing a pcb for extended periods of time, it is left unattended. In some cases, the board can indeed reset but you may not be able to detect it if you only check on the pcb occasionally.
I thought that in these cases, I would like to know if the game has indeed reset. This is important information to have for repairs. The idea would be to capture a trigger event from the watchdog circuit. This could be a logic high to low (reset) to high (if the game boots again) transition.
I decided to purchase a triggered timer pcb with an LED display. The specific one is below and has a trigger (when GND) and a reset (also when GND).
$12
https://a.co/d/iVFKl3p

The experimental test board is an annoying OutRun pcb that always give me issues. Power hookup to the counter was a snap, using the 5V line. I placed a IC grabber on the MB3771 IC (watchdog reset IC on the main board) and hooked up pin 8 (reset line) to the trigger terminal of the counter.
When the game runs correctly that pin is at a logic high and goes to GND during a watchdog reset.
My test worked, I could track the resets on this pcb despite the game producing no video. Here is a video of it below, notice how the counter advances on every trigger event (I used a logic probe to make the trigger audible).
Overall, a quite handy tool (for me anyway) and fairly inexpensive to make.
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