10 Aug
2019
10 Aug
'19
10:56 a.m.
On 08/09/2019 11:05 PM, Douglas Taylor via cctech wrote:
I have a question about cable length - any electrical
engineers in the house?
Connected a Qualstar 1260 tape drive to an Emulex TC02
qbus tape controller in a pdp-11/53. The interface is
pertec with 2 50 pin cables.
When I use a pair of short flat ribbon cables, 18 and 30
inches each, it works. Under RT11 I can INIT, Copy, DUMP,
do a Directory.
It doesn't work when I use a pair of 5 foot long flat
ribbon cables. Are they too long? Do I need twisted pair
type of cable? Is it possibly a termination problem?
I have used cables about 20 feet long without trouble. The
2 50-pin cables is the Pertec formatted interface, which is
really forgiving. Does you drive have terminators in both
ends of the cable (both at the TC02 end and the drive end)?
Now, I will mention that I have ONLY used twisted-pair
ribbon cables with both flavors of interface, never straight
ribbon cable.
Jon