I have a client with an iDCS 100, Had a major storm come through and power went out in the neighborhood. The system is Grounded and was on a power/surge strip. The PRI from Comcast checks out OK. When it is powered up there are no lights on the SVMI4, the PRI Card or the Mem card. BUT the phones light up and say REV V2.1

Did the power supply go bad or the back plane?

Check the fuses in the power supply. I think there are 3 of them.

Checked those. All 3 are good.

I would suggest that the power supply is your problem.Although I have seen an MCP1 card taken out upon a power up.

If you service 100s, you MUST keep at least 1 and best 2 power supplies on hand.

The power supplies were built with underpowered capacitors and will last awhile but there are 4 that get replaced when repaired, not just the two big ones.