DEC rack-mount AlphaServer 2100A

If there's anyone out there with a rack-mount DEC AlphaServer 2100A - the one with the underslung pair of power supplies -- I'd appreciate your help in determining the 15-pin control-cable configuration for J3. It may require examining the other end of the "power supply control cable assembly" P#17-04014-01, which is 24-pin (to handle the dual/redundant power supply configuration). Available hardware documentation is pretty sparse. Physical examination of an AlphaServer 2100A system backplane (54-24129-01) would certainly help! While I'm pretty sure that I've figured out the +5V +- sense lines (pins 3-4), and the +3.3V +- sense lines (pins 15-14), I've failed to determine the purpose of other control lines - most particularly which one(s) turn it on. Pins 10 is suspect, but there's no obvious reference point for voltage measurement or evidence whether it should be shorted to another pin, or . something else. There's no control relay or other obvious mechanism. The PCB is dense-packed with surface-mount components on one side and power components on the other; tracing circuits is a bear. Applying AC starts up the 24VDC fans, but none of the four switchers kick in :-<. Thanks for any clues! paul