need help on PDP8/a

Does anyone know a reason why I can't remove the G8018's and G8019 and replace them with newer OEM power supplies? I know that one G8018 supplies 5V @ 25a, +15V @ 2a, -15V @ 2a and +20V @ 4a. I believe the 20V is only used for core memory. So.a 5v supply @ 50a should be sufficient, and a 2 dual output +/- 15v supply @ 2@ each should be a reasonable substitute. I am aware of the functions of the G8019 and that I would be defeating the "dead fan shutdown" and battery backup feature. OR. Does anyone have a written procedure for troubleshooting the backplane, specifically the SC260m triac, the opto isolator, the 2n6531 transistor and what causes the 47 ohm resistor to burn. With all boards removed I know how to defeat the removal of the two G8018's and on a good backplane by adding a jumper between two pins on the G8018 connectors. I can apply 3v to a pin on the G8019 connector to get the triac to fire. But this is not enough for troubleshooting a bad backplane. All help will be greatly appreciated. Thom Melbourne Florida