Hi Ken,

It sounds to me as if the backplane is hosed. If a visual inspection
doesn't show any problems then perhaps the short is within the layered pcb
itself. Alternatively, perhaps one of the decoupling/filter capacitors has
gone short-circuit...

> Now, there are 4 3-pin jumper headers on the board, with 1-2 labeled A & 2-3
> labled P.  All are straped to P.

Those are the bus termination jumpers. A = Active, P = Passive.

> There is also a 5-pin header labeled from
> the top SYSRES, SYSFAIL, ACFAIL, +5V, GND.  Nothing is attached to this
> header.

I suspect these just repeat the VMEbus signals of the same name so they
can be brought out to an LED panel on the front of a rack.

> So...any clue what I've done wrong, or did I get a pair of duds?

Looking at the specs for the J1 backplane on Schroff's website, a nominal
resistance of 5 ohms between 5V and Gnd looks about right when passive bus
termination is enabled. Therefore, I suspect at least one of your boards
is fine (at least in the 5V/Gnd department ;-).

HTH.

Cheers, Steve