>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@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