Our school recently got an old IRB4400 with S4C+ M2000 controller. There seems to be several of the 24V supplies missing, including the one to the CPU. (Measured at the contacts at G1) It has been in storage for some years, storage conditions unknown. When I first powered it up, there was a red LED on the PSU (AC OK) but no lights in the CPU, after a few attempt to power on with or without the harness plugged in, I got the green light, but still no CPU lights. Now it's back to red and there are no 24V to cooling, SYS or computer.
Are there any info available to help troubleshooting the PSU electronics? Since we don't know the condition of the rest of the cabinet, we are somewhat reluctant to spend a lot of money on a replacement PSU.