VAX 4000-500 PSU Overload?

Robert Jarratt robert.jarratt at
Sun Dec 13 09:46:55 CST 2015

> -----Original Message-----
> From: cctalk [mailto:cctalk-bounces at] On Behalf Of Holm
> Sent: 11 December 2015 07:42
> To: General Discussion: On-Topic and Off-Topic Posts
> Subject: Re: VAX 4000-500 PSU Overload?
> There is a big rectangular Cap in that PSU that I've left there since
> I don't have a usable Replacement and the primary caps where still good so
> far. The PSU itself is a really bad design from sight of repair, you can't
> properly replace the caps on the switcher PCB since you could'nt dismount
> the heat spreader so I suggest that you pull the Caps from above and
> new one from above as I finally did.

I have been able to remove the leaking ones from the +12V and -12V board, I
just have to wait for the new parts to arrive. The two on the 5V and 3.3V
board have not leaked, are not bulging, and are harder to remove without
removing the bottom heatsink or pulling from above as you suggest. I have
not been able to reach them with my ESR meter either, unfortunately. I am
tempted to leave them, although pulling from above is an option. Does anyone
else agree with the pull from above solution? In case you have not seen it,
the design makes it very hard to get at the underside, you have to desolder
a load of transistors to do so, and they are not in easy locations either.



More information about the cctalk mailing list