Opening a DECserver 90M External PSU

Robert Jarratt robert.jarratt at
Fri Oct 16 11:46:45 CDT 2015

> -----Original Message-----
> From: cctalk [mailto:cctalk-bounces at] On Behalf Of Peter
> Coghlan
> Sent: 15 October 2015 23:47
> To: General Discussion: On-Topic and Off-Topic Posts
> Subject: Re: Opening a DECserver 90M External PSU
> 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
> 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
> 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
> 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...
> Regards,
> Peter Coghlan.

I tried to pry mine open, but it seemed that if I kept going I would end up
damaging it more than I would like. Do you have a picture of the opened
casing I could see? That would help me to see how best to open it.



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