Opening a DECserver 90M External PSU

Peter Coghlan cctalk at
Thu Oct 15 17:46:31 CDT 2015

Back in April, I wrote:
> Robert Jarratt wrote:
> >
> > One of my DECserver 90M PSUs got dropped and stopped working as a result,
> > possibly because it got pulled by the cable. That sounds like the kind of
> > damage that might be repairable. I tried to open the enclosure and I found a
> > hole under one of the labels, expecting it to be a screw hole, but it isn't.
> > I am guessing you just have to pry the halves apart, but without knowing
> > where the clips are inside it is easy just to break the thing.
> >
> > 
> >
> > Does anyone know how you open these PSUs?
> >
> As far as I recall, there are no clips - it is glued all the way around.
> Mine (actaully a 90TL, with H7082-AB PSU) failed too.  Using a lot of patience,
> I pried it open without too much damage, fixed it (a capacitor in the startup
> circuit IIRC) and glued it back together.  The end result was only slightly
> rough looking and would probably have been better with a more suitable glue.
> The thing has a very Lego-like quality about it.
> It failed again some time later and I haven't had the enthusiasm to break it
> open again since.

I finally worked up the enthusiasm.  It was easy to open this time as the glue
I used to put it back together last time was not so good.  While I was measuring
voltages on the input side, out of the corner of my eye I noticed the LEDs on
the front of the terminal server lighting up briefly.  I found that I could get
them to light up consistently by pressing a meter probe on one of the legs of
the chopper transformer and after deploying the magnifying glass, I found a tiny
crack in the print leading to it.

That was a lot easier than I thought it was going to be.  I hope it lasts a bit
longer this time though.

Now I find that the privileged password is not what I thought it is...

Peter Coghlan.

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