Powering up a 20-year old MicroVAX II

Robert Jarratt robert.jarratt at ntlworld.com
Sat Feb 28 08:23:50 CST 2009

Thanks for all the replies over the last few days. I am sorry I have not
replied to them, I have been away for work all week (and will be away again
over the next few weeks). I thought I would gather up my various responses
into one email, so here goes.

To the person who asked about the enclosure. This is a BA23 and has only one
PSU, so without that PSU I cannot try to get the machine running again.

The harness I have is not the same as either of the two that someone sent me
pictures of. It is not a ribbon cable, it has discrete wires, of different
lengths, its part number is 70-20450-01, rev C1 and there is a date of 9th
Dec 1985 on it. The actual connectors though look like the connectors on the
bad ribbon cable harness, I think they are MTA-156.

Some have suggested it blew because I had insufficient load. I had a TK50
and an RD53 attached, would that no be sufficient. Furthermore I did not
actually switch the PSU on, just connected it to the mains, would the load
connected to the PSU matter when the PSU is not actually switched on?

There was also a suggestion that the PSU would have needed switching
separately for 50Hz operation as well. The hardware manual I have for the
machine tells me how to switch between 110 and 240, but does not say
anything about switching it for frequency, so I suspect this was not an
issue here.

>From the various responses I think it would be unwise for me to attempt a
repair. Is there anyone on this list who is in the UK who would be willing
and able to fix this PSU, or who knows someone who might be?



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