Powering up a 20-year old MicroVAX II

Robert Jarratt robert.jarratt at ntlworld.com
Sun Feb 22 08:48:59 CST 2009

> Correct the worng harness has unequal length wires and the correct
> one has equal length wires.  The harness in question goes from the
> Backplane to the PS.
> The problem is with unequal length wires the connectors were sharing
> the
> load unequaly and the connecotr would overheat and fail sequentially.
> It was more of a problem on highly loaded boxes.
> >Field service were (again, iirc) supposed to swap these out if
> >they came across them. But if your machine has truly not been used
> >for twenty years, it ended up in storage relatively eraly in its
> >life and so may not have had a chance for some FS TLC.
> 20 years is maybe on the wire.  It may have been already replaced.

The harness in my system does not seem to match any of the descriptions I
have seen so far. The wires are not equal in length, but it is not a ribbon
cable with IDC connectors either. The connectors are black rather than
white. The harness wires do not seem discoloured, but I believe that this
particular system may have only had light use in its day. I have a picture
of the harness but I am not sure if the rules of this list allow

The system has a CPU card, two memory cards, three "half height" controllers
(disk, tape, async i/O), and a full height third party external expansion
storage card. I have the expansion storage box too, but to keep load on the
PS down I would be happy to remove the extra card until I make or get a new



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