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Title: Nichibutsu Frisky Tom 6.3VAC Bypass? Post by: ataritoobin on June 09, 2010, 04:02:08 AM I have a couple of Nichibutsu Frisky Tom PCBs that when hooked up to standard +5VDC and +12VDC exhibit the same issue.
They will boot and pass both RAM and ROM tests, then promptly reboot. Both will boot to the test mode and play music, sound effects, etc. The PCB appears to take 6.3VAC at input 10 and 27 on the edge connector. On the schematic it looks like this goes through a NE555 timer / some sort of clock circuit (5O chip on schematic is a SN74193N, 5N is SN74LS74AN) to kick in the custom CPU reset. I tried hooking up a 6.3VAC transformer, but the voltage was a little off (a little above 7VAC I believe) and got the same results :25- I've attached a snippet of the schematics - is there a way this circuit could be modified to use standard voltages? Thanks! -Steve |