Have you checked the 48V out of the power supply? I don't know the inside of those units, but I know the 48V is generated as one of the voltage rails in the PSU, and they are cabled into the main chassis.

Depending on how confident you are about debugging hardware, it could well be possible to loosen the housing on the power connector and slide the cover back down the cable, exposing the pins. From there, you could go round the connector pins taking voltage measurements using the +ve probe your multimeter with the -ve on the PSU chassis.

thanks. will try.