Microvax II 'primer'?

[Adrian Graham]

>At this stage I've got no idea if it's a SMPSU or a linear (I've not
popped the panel off)... I suppose if it's linear then it perhaps doesn't
even need a load to do its thing. If it's a switcher then I expect it'll at
least need something on +5V, and maybe +12V too (unless it has built-in
load resistors to keep the regulation happy, as designs occasionally do).

It's actually 3 separate boards and 2 identical discrete PSUs for +12 and
+5 in a massive metal box, the thing is a beast and fits along the whole
side of the machine behind the Q22 backplane.

Cheers

A

On 22 January 2018 at 13:43, Jules Richardson via cctalk <
cctalk at classiccmp.org> wrote:

> On 01/21/2018 04:04 PM, Rob Jarratt wrote:
>
>> You might find that the filter capacitor goes up in smoke soon after you
>> connect the PSU to the mains, even without powering it on.
>>
>
> Yes, Adrian Graham mentioned that (via FB), too. I seem to have extremely
> good luck with the RF filter caps, unlike other people, but I'm always
> prepared for the cloud of smoke :-)
>
> Otherwise it is certainly wise to check the PSU visually for any obviously
>> failed electrolytics. If  you have one of the DEC load boards you could
>> connect the PSU to that as a dummy load. I don't think there is much in
>> the
>> way of dependency on the CPU to run the PSU.
>>
>
> At this stage I've got no idea if it's a SMPSU or a linear (I've not
> popped the panel off)... I suppose if it's linear then it perhaps doesn't
> even need a load to do its thing. If it's a switcher then I expect it'll at
> least need something on +5V, and maybe +12V too (unless it has built-in
> load resistors to keep the regulation happy, as designs occasionally do).
>
> I see on the output rating label that it lists connection points for
> different outputs, so maybe I just need to slap a couple of suitable
> resistors onto the +5V and +12V outputs so that they draw an amp or so, and
> see how it goes.
>
> Once you have the machine up and running...
>>
>
> Lets not get ahead of ourselves ;-)
>
> I am not sure if 4MB is enough to do that though.
>>
>
> Hmm, one of the things that I'm clueless about right now is how the bus
> evolved over the years - I've still got a pile of Q-bus boards which I
> saved from a recycler last year, and I know there's a 4MB board (made by
> Clearpoint, if I remember right) among them. But if that's designed for
> earlier PDP hardware then it's possibly no use whatsoever in a Vax world...
>
> cheers
>
> Jules
>
>


-- 
adrian/witchy
Owner of Binary Dinosaurs, the UK's biggest home computer collection?
www.binarydinosaurs.co.uk