On Sun, Dec 5, 2021 at 11:46 PM Josh Dersch <derschjo at gmail.com> wrote:
I swapped boards around in the datapath for these bits
on the TC01 side
last night and the problem doesn't move. On a whim I put my thumb on the
tape as it passes over the head and it seems to affect the glitchiness of
the data, at times making it appear to go away entirely. Doesn't appear to
be a tape tension problem -- it seems adequate and putting my thumb on the
supply reel to increase tension a bit does not have the same effect. This
would seem to point to the TU55 being the issue, and quite possibly the
heads. I haven't had time today to look at the signals coming off the
heads but I plan to soon.
Thanks for the help!
- Josh
I would measure the resistance of the head coils at the relay board
connector. Hopefully they all measure about the same. Figure 2-2 in the
maintenance manual shows how the MARK and DATA tracks are wired, and the
extra connection available for the TIMING track. We found a head on the
PDP-9 where the +D0 connection was open.
--
Michael Thompson