12 Oct
2015
12 Oct
'15
11:29 a.m.
We swapped the TU56 and TU55 drives between the PDP-12
and the PDP-8/I. We
Does the TU55 work correctly on the 8/I ?
The TU55 behaved a little better than the TU56, and
sometimes would
actually boot OS/8. We continued chasing the issue and found glitches on
data channel 3. We have swapped every module and cable that relates to data
What exactly do you mean by 'glitches'? Are these on a TTL level signal, an
analogue
output of the read amplifer, or what?
Have you looked for glitches on the other data channels?
channel 3, but have not been able to fix the glitches.
The glitches are
there with both the TU55 and the TU56, so the problem is in the TC12
controller.
IIRC this thing has 3 data channels, so is channel 3 on the outside of the head/tape?
Could it be some external interference that happens to be picked up most strongly
by that head winding?
-tony