Over the last few months, I've put together a batch of VME gear to run 
NetBSD on (2xMVME164, Heurikon Nitro260, possibly an MVME177, memory cards, 
SMD controllers, SCSI controllers, racks, etc.).  I also picked up two new 
(supposedly) Schroff 4-slot VME backplanes (model 23000-464); very 
impressive physical construction.  Unfortunately, I'm having some problems 
with them.  It's probably because of my ignorance of VME, and the slim doco 
they came with. 

Basicly, I've got them in a rack with another, known-working, non-Schroff 
backplane.  When I apply power (+5v & GND) to the Schroff backplanes, they 
short the power supply (or rather, the PS detects the short an doesn't come 
on line).  Using an Ohmmeter confirms that +5v to GND has no resistance.  
The known working backplane has about 5 ohms between +5v & GND. 

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

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

Many thanks... 

Ken