PDP 11/45 partial success.

Jim Beacon jim at g1jbg.co.uk
Fri Mar 18 14:42:29 CST 2005

Hi All,

after a few days frustration, I have got a little further with my 11/45.

The power supplies checked out OK with respect to ripple and output, but a
couple have them have the odd VERY fast spike on them - is this normal? (I'm
using a 100MHz 'scope - I suspect they may not be visible on a slower one).

After reducing the machine to its basics, I found I could load an address
from the front panel, but not write or examine any location successfully.
The address and data lines became active, but the processor then goes into a
pause state. I found that the MSYN line was not being asserted, and it
appears that one ic on the Unibus controller (M8106) is not providing the
correct ouput - grounding the scope probe will force the line, and the
processor completes its bus cycle (Yes the inputs to the ic are correct!).

I have found a spare serviceable UBC, so I'll try that when I next get
chance, and if that fixexs the fault, I'll repair mine.


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