I forgot that the diagram says the H754/784 AC input
connectors are white :p
I am now trying to work out how the colour of the connector can have any
bearing on the voltage you measure!
[YEs, OK, I did once see measurements that showed that black plastic
boxes were more electrically leaky than the equivalent white ones --
presumably the black colouring contained carbon or something. But that
was working with voltages of 10's of kV, and currents of nanoamps. Not
applicable to the PDP11 PSU]
-tony