Powering up a 20-year old MicroVAX II

Tony Duell ard at p850ug1.demon.co.uk
Mon Feb 23 14:47:07 CST 2009

>    I haven't been into a BA23 PSU, so this is a question, not a 
> suggestion - does that PSU have a separate "jumper" plug for 50Hz/60Hz 
> switch?

SInce the first thing an SMPSU does with the mians is rectify and smooth 
it, it's not going to care about the mains frequency. And no sane 
manufactuer would ever design one where any auxilliarly supply (e.g. to 
get the main SMPSU started) would care about the frequency either.

>    I toasted an RA60 once by just flipping the visible switch from 240V 
> to 110V, not knowing there was a separate physical setting to switch it 
> from 50Hz to 60Hz.  The behavior as it burnt up was just like this.

Tje things that really care about mains frequency are ferroresonant PSUs 
(sued, for example in the DEC RX01 and RX02 drives) and disk spindle 
motors. I am very suprised an RA60 was damaged by having the frequency 
set wrongly, any idea what parts actually failed?


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