On Sun, Dec 5, 2021 at 11:46 PM Josh Dersch <dersc...@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
