Just finished fixing a Stargate board that was coming up with an adjustment failure every time it was powered up. There were two things odd about the board. The first was that someone had jumpered diode D9, which would have the effect of trying to power the board off the batteries or maybe somebody thought they could put NiCads in and recharge them. Anyway, it was not useful so I removed it. The other odd thing was that they had removed the pullup resistor R43 which would cause the input to the NOR gate at 6E to be indeterminate or low, basically making it as if the memory protect switch was pressed all the time.
After replacing the resistor, the gate was showing the input as low on the memory protect switch pin so I knew the NOR gate was bad. I removed the chip and put a socket in and replaced the chip. When I powered up with no ground on the memory protect pin (the equivalent of the coin door being open), the three messages flashed without the warning:
Press advance and it was game on, we have a working Stargate again:
I did circle around and jumpered the memory protect pin to ground (coin door closed) and it did give the adjustment failure message, just the way it was supposed to.
I love it when a plan comes together
ken
After replacing the resistor, the gate was showing the input as low on the memory protect switch pin so I knew the NOR gate was bad. I removed the chip and put a socket in and replaced the chip. When I powered up with no ground on the memory protect pin (the equivalent of the coin door being open), the three messages flashed without the warning:
Press advance and it was game on, we have a working Stargate again:
I did circle around and jumpered the memory protect pin to ground (coin door closed) and it did give the adjustment failure message, just the way it was supposed to.
I love it when a plan comes together
ken
