It certainly isn’t on the second PCB. That’s the power supply and I’d definitely keep my hands off that. YOur best chance is to look for an IC with “555” in its’ type number. That’s the most commonly used timer chip. Search the net for a data sheet for the specific type and find the right pin to ground. It should be the one to start the timer; depending on the way the timeout is implemented it might also be the “set” pin.