J
JW
The schematic located in the service manual for this power supply has a
logic error: on page 128 (BIAS SUPPLY) it shows that U11 pin 1 (DELAY) is
connected to the micro's reset pin. This is incorrect. U11 pin 5 (RESET)
should be connected to the micro's reset pin. I have verified that this
error also exists in my power supply - it is mis-wired/routed. I've
re-worked my power supply to correct the issue when it had stopped
working, but the LM2925T's RESET output does not drive to a proper logic
1. It only gets to about 2 volts. The problem is that the LM2925T's
internal pull-up is only 30K. Since it is driving a 80196 as well as an
ASIC, this was not quite good enough. Solution: I added an external 4.7K
resistor to the micro's reset line. The power supply is now operational.
logic error: on page 128 (BIAS SUPPLY) it shows that U11 pin 1 (DELAY) is
connected to the micro's reset pin. This is incorrect. U11 pin 5 (RESET)
should be connected to the micro's reset pin. I have verified that this
error also exists in my power supply - it is mis-wired/routed. I've
re-worked my power supply to correct the issue when it had stopped
working, but the LM2925T's RESET output does not drive to a proper logic
1. It only gets to about 2 volts. The problem is that the LM2925T's
internal pull-up is only 30K. Since it is driving a 80196 as well as an
ASIC, this was not quite good enough. Solution: I added an external 4.7K
resistor to the micro's reset line. The power supply is now operational.
