Ok, so I have managed to find my way back into the apple collecting hobby accidentally. 
I have since aquired an Apple IIgs that when I turn it on, I get Fatal System Error 0911. I know that the error has to do with ADB. I am going to try the lightbulb over the ADB chipset trick. I also have checked all the PSU voltages and they are within half a volt. Have I missed anything? The machine in question appears to be a ROM 0 upgraded to ROM 1, and I have tried it without anything else connected, and the memory board removed. Anything else?
I have since aquired an Apple IIgs that when I turn it on, I get Fatal System Error 0911. I know that the error has to do with ADB. I am going to try the lightbulb over the ADB chipset trick. I also have checked all the PSU voltages and they are within half a volt. Have I missed anything? The machine in question appears to be a ROM 0 upgraded to ROM 1, and I have tried it without anything else connected, and the memory board removed. Anything else?