pages 43 and 84 of the UDA50 engineering drawings
contain
 pinouts of the 32 pin connector for the coax SDI cables, for
 those brave enough to
 try;)
 I'm assuming that the "L" sides of the pulse transformers
 correspond to the coax shield.
 
http://www.bitsavers.org/pdf/dec/disc/UDA50/MP01331_UDA50_EngrDrws.pdf 
Page 43 is the important one since it details the connector, but AFAIK it's
not coax, it's a ribbon cable, though I guess the principle is the same. You
could get a correct result using chopped up IDE cables perhaps......
cheers
a