10 Feb
2013
10 Feb
'13
11:46 a.m.
Although I can set and reset the two drive select bits
on the RL8A,
and the 75113 line drivers also change state appropriately, those
I asusme you mean that the outputs of the line drivers change state. If
you're only checking the inputs, then the line driver might habve failed
signals are not reaching the correct place on the
logic board inside
the RL02! At the 75107 line receivers (E57), those two bits are always
I assunme (again) you checked the outputs of the line drivers on the
RL8 controlelr with the cable and drives conencted. Just in case a short
somewhare is killing the signals.
So, you've got signals changing at one end of a bit of cable, not at the
other. Have yoy checked for continuity? Have you made sure there's not a
danaged pin in the conenctor.
logic 00, i.e. drive 0. So the drive won't select
at all unless I put
the Unit 0 plug in, at which point it effectively ignores the drive
select bits and always selects regardless of the state of those two
bits at the controller. Confirming that the drive select lines are dead.
The only thing between the line drivers and receivers is 6' of ribbon
cable. It leaves the RL8A on J1 header pins TT, SS, RR, PP and is
supposed to enter the RL02 logic board on J12 header pins C, D, E, F
which accounts for the cable being reversed. Just in case I even tried
flipping the header connector around and of course the drive won't
load or work at all and the Fault light stays on, so I know I have it
facing the right way. Unless it's possible to make a cable upside down
and backwards, or some such?
I think if you're mad e the cable backwrds, then the drive 'energiser
clock' is missign nad the drive Faults all the time.
What exactly do you ahve i nthe way of cabling/connectors? The normal RL
drives have a pair of DEC zero-insertion-force conenctors on them. How
have you linked your ribbon cable to that?
I can't think of anything that could
"lose" the drive select lines
except a defective cable (will continuity-check tomorrow, even though
I made a new one by copying the old one that used to work) or else the
correct cable (BC80J-20) is not a straight-through pin for pin
connection, in which case I have to have one.
DO you have the printset f othe controller and drive? Surely you cna
find the pinotus there and see ifhtey match up. Or use your continuity
checker to trace the signal from the output of the line driver to a pin o
nthe berg header, up the cable, to a pin on the RL02 logic board, then
see if that makes sense.
-tony