12 Dec
2017
12 Dec
'17
5:01 a.m.
On Dec 12, 2017 3:41 AM, "Mattis Lind via cctech" <cctech at
classiccmp.org>
wrote:
There has been plenty of good suggestions already.
If I were you I would:
1. Check voltages from the PSU as mentioned previously.
2. Check AC LO / DC LO signals as Bill mentioned.
3. Strip out every card on the bus except of the terminator boards and the
M7859 programmers console.
4. Put the console in maintenance mode and check that the BUS itself is
OK.
(http://retrocmp.com/tools/pdp-1134-programmers-console)
5. Add more cards, like serial board M7856 or whatever and then use the
programmers console to probe it.
6. Add memory and check a few locations from the programmers console.
7. Add the CPU and check that you can read the PSW register at 777776 and
the internal registers starting at 777700.
Since the programmers console has its own 8008 on board it is a quite
powerful tool to diagnose the Unibus and the peripherals even without the
CPU is present or running.
But note that the M7859 might fail. One of my M7859 had failed and it took
a while to repair. OC drivers, flip flops and registers was bad. Here is
my
story :
http://www.datormuseum.se/computers/digital-equipment-corporation/pdp-11-04…
Here's one more... if possible find a working 11/34 and perform a
diagnostic procedure or measurement there and take notes, then repeat on
your system. That, and swapping known-working boards when available will
help pinpoint problems where they exist.
Bill