11/34 sanity check

Josh Dersch derschjo at gmail.com
Fri Apr 24 23:32:38 CDT 2015

While I was waiting for the Ridge's disk to dump over a 9600bps serial 
port, I finally got a chance to work on my 11/34.  Picked it up last 
summer and it was in good shape but the power supply was completely 
dead.  I've rebuilt the supply and last night I worked out the last few 

So at this point all voltages are spot-on, the AC LO and DC LO signals 
are high (these are active low, right?) but I can't get the machine to 
respond at all -- the "DC ON" and "RUN" lights are lit up brightly, and 
the "SR DISP," "BUS ERR," and "MAINT" lights are glowing dimly.  The 
status register display is dark.  The system does not respond to any 
keypresses on the panel.

I'm getting better with UNIBUS stuff but I wanted to run this past you 
guys before I whip out the debugging tools and start tracing things.  
I've taken it down to a pretty minimal configuration, sans any memory or 
other stuff.  Here's what I have in the main backplane (all others are 
disconnected for the time being) from right to left:

Slot 1: M7266 (CPU)
Slot 2: M7265 (CPU)
Slot 3: (AB) M9301 (bootstrap terminator) / (CDEF) M7859 (front panel board)
Slot 4: empty
Slot 5: empty
Slot 6: empty
Slot 7: empty
Slot 8: empty
Slot 9: (AB) M9302 (terminator)

The "empty" slots have Grant Continuity boards installed and the NPG 
jumpers on CB1-CB2 are all present on the backplane.  I've confirmed 
that all the right voltages are making it to the backplane (and I've 
cleaned up those damned Molex connectors as well, just to be sure). Is 
there anything I'm missing?  Anything I should try?  Does this failure 
mode sound familiar at all?

Thanks as always,

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