VAX 11/750 power supply fault

[J Blaser]

Quoting Tony Duell <ard at p850ug1.demon.co.uk>:

> But I can be eaily persuaded to look at the PSU schematics sometime and
> see if I spot anything obvious. Or at least tlak you through the design
> (which might be somewhat unconventional if other DEC supplies are 
> anything to go by [1])
> 
> [1] This might not be a problem for you. If oyu don't have any experience 
> of SMPSUs, any one is as good/bad as another to get started with. The 
> problems generally come if you have fixed ideas ofg how supplies should
> work and then you get something strange thrown at you.
> 


Thanks much for the offer to work me through this!  There are a couple of things 
that I want to do tomorrow night when I get a chance.

Clint's suggested that there is something 'shorting' the supplies outputs has 
prompted me to consider disconnecting all outputs (+5V, +/-15V) from the 
backplane, and *only* hook up my auto headlamps as a load.  I don't know that 
this will give me anything useful, but I'll give it a try.

Based on those results, I might be ready to cry, "Uncle!" and ping you for some 
advice.  I do like Clint's suggestion to solder some wires to various points, 
bringing them to the outside for measurement (that's just the sort of thing I 
would not have thought of...thanks, Clint!), so that might be a good next step.

More soon (after my only-headlamps-connected test)...

- Jared