PDP 11/45 partial success.

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. Jim. Please see our website the " Vintage Communication Pages" at WWW.G1JBG.CO.UK