Powering up a 20-year old MicroVAX II - test-drb@ccmp.vtda.org

23 Feb 2009

Robert Jarratt wrote:
...
  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
 attachments.
    The key point of your description is that the wires are not equal in 
length. This COULD be a bad thing.

I have a BA23 chassis that had a melted power supply connector. The 
connectors were AMP MTA .156 IDC connectors with individual wires. The 
connector housings were Yellow. The failure point was the connection 
between the harness and the power supply pin.

As Allison describes, the problem is that there was an unequal 
distribution of current between shared pins. I replaced the harness with 
one that I made myself using high current box connection pins... with 
equal length wires.

There is a field service notice that describes the problem and even 
mentions the color of the connectors. I remember reading it and saying 
to myself that was my chassis. I just can't remember where...

-chuck