22 Jan
2018
22 Jan
'18
8:49 a.m.
On 01/22/2018 07:43 AM, Jules Richardson via cctalk wrote:
On 01/21/2018 04:04 PM, Rob Jarratt wrote:
All VAX and uVAX main power supplies are switching types.
If you see an electrolytic cap in there with a 200+ V
rating, that's a certain giveaway of a switching supply.
Jon
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).