Odd problem with GE versamax

[nswu1]

Check this out , got a call to check out a versamax with cpu001. Here was the initial symptom, powersupply had 24vdc as it should but no lights on cpu. I also noticed the port1, and port2 cables were unplugged. I plugged them in the cpu powered up. I was then able to communicate and dump in program and clear faults. As I continued on I unplugged the power plug on a Siemens mp370 and all cpu lights went off, never lost power to power supply. They had a spare cpu and power supply. I changed them and dumped in program, all now works. The power supply is toast, first time I ever seen cpu power up from external device on comm ports.