21 Jul
2012
21 Jul
'12
12:44 a.m.
Spent a few hours today with the unibus documentation, meter and scope
and have concluded there are no breaks in the NPG / NPR / BG4-7 or
BR4-7 lines on the 9 socket backplane.
It is possible that some of the HALT / Bus Error problem might be with
the KY11-LB.... some of the keys on the keypad don't return the
correct values on the display when pressed. Specifically 3 and 6
which cause the display to show 1 and 4. These happen to be on the
same READ cycle as the CTRL and DEP buttons. My initial thought was a
problem with the 7404 that controls the READ signal but that looks OK
on the scope. I will pull the keypad off tomorrow and make sure it
isn't something in the switch matrix.
Not sure if anyone else has seen similar issues with the KY11?
I need to get back to the M7856 serial cable and replace the Molex
with a DE9 (well spotted Tony... I never realized that DB9 was not the
right name). It may be that the machine is powering up fine and the
console emulator works even if the KY11-LB is misbehaving. Will try
that tomorrow.
Tony - to answer your question.... the 6 pin molex had 2 ground pins,
RXD, TXD. Also RTS and DTS are wired back to the Berg connector. I
thought I read somewhere that these are not used.
On a positive note... all the power supply voltages on the backplane
looks good after the rework on those.