On Dec 12, 2017 3:41 AM, "Mattis Lind via cctech" <cct...@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---s-n-ag03092
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
