there are several problems. I took the pcb to my workplace where I plugged another psu and jamma bundle into it, there was no short circuit because there is no one connected to the jamma connector other than the RGB and power supplies. there was no short circuit just at home. i put this pcb aside a bit because it is messed up here all ....
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Hi again.
I managed to start it based on the pinout.
I got my hands on a Tutancham pcb again.
It produces a strange error. I believe that another pcb of the same type sometimes did this at startup. but this other one won't start even once. there might be some small mistake, I don't know where to look. maybe someone has an idea?
I read the eproms, they all have the same original checksum.
Thanks if you can help me in any way.
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ShootTheCore
Legendary
It looks to me like the board is stuck in a watchdog loop, which means the CPU is crashing from bad code. If you have a logic probe or oscilloscope, probe pin 37 on the 6809 CPU - that's the RESET line and you should see it go Low briefly every time the watchdog barks and board reboots.
If a watchdog loop is indeed what's happening then you need to figure out why the CPU is crashing - since you've verified the ROMs are good, I'd look at the CPU work RAM chips next.
If a watchdog loop is indeed what's happening then you need to figure out why the CPU is crashing - since you've verified the ROMs are good, I'd look at the CPU work RAM chips next.
Thank you very much for your answer.It looks to me like the board is stuck in a watchdog loop, which means the CPU is crashing from bad code. If you have a logic probe or oscilloscope, probe pin 37 on the 6809 CPU - that's the RESET line and you should see it go Low briefly every time the watchdog barks and board reboots.
If a watchdog loop is indeed what's happening then you need to figure out why the CPU is crashing - since you've verified the ROMs are good, I'd look at the CPU work RAM chips next.
I checked the Ram and checked it with Eprom Burner RAM test function. RAM is fine.
I checked the reset pin of the CPU with a logic probe. after switching on, it remains at the LOW level for a moment, then at a continuous HIGH level.
