Revive 11/34

william degnan billdegnan at
Tue Dec 12 07:01:34 CST 2017

On Dec 12, 2017 3:41 AM, "Mattis Lind via cctech" <cctech at>
> 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
> (
> 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
> story :

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.

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