Viking SCSI controller secrets?

Hi everyone, Is there some secret lore about Viking SCSI controllers that I need to get them to work? I've got a Viking QDT (dual wide Disk and Tape) that has V1.5 of the firmware. When I plug it into my VAX with two RZ55's in an expansion cabinet and type SHO DEV (MV3500) it says: UQSSP Disk controller (177xxx) -? Then finds the TK70 and adds UQSSP Disk controller (xxxxx) -? Its not exact but basically the system knows I've got an MSCP disk controller and a second TMSCP tape controller and when it asks them what devices they have attached the Viking seems to be answering ("I don't know.") Now if I hook it up to a box that had a couple of MO drives in it (an old Aspire cabinet) then it reports DUA0 (@0) and DUA1 (@0) and no tape (as expected, and it doesn't even print the -?) I don't have the funky cable to get to the RS232 port (although the Aspire box does, it doesn't seem to work correctly) Questions: 1) If I build a funky cable, which three wires do I use? 2) Shouldn't it just work? --Chuck