Opening a DECserver 90M External PSU

Peter Coghlan cctalk at
Fri Oct 16 17:45:05 CDT 2015

> Thanks very much for this. Interesting that there is a fuse inside. You
> would think the casing would be designed to allow the fuse to be replaced
> somehow.

That's not the original fuse either.  I managed to blow that one when I was
trying to find the original problem with the PSU.  I was having a really bad day
and I somehow managed to clip the scope ground lead onto the negative end of the
rectified mains smoother instead of the negative of one of the output smoothers.
The original fuse had wire ended caps pressed on to it and I was unable to
get them off so I ended up soldering loops of wire around the replacement fuse

It looks like the case was originally designed to be held together with a single
screw.  Perhaps it was later decided that this was insufficient to keep it from
coming apart and exposing dangerous voltages if dropped from a height and it
was decided to glue it together instead?

I can sort of see why it might not be a priority to make the fuse replacable.
Firstly, someone might try to replace it with a 13A plug fuse.  Secondly, if
the fuse did blow, there would likely be other components damaged.  Sadly, it
might be cheaper to get a replacement unit from stock than to pay someone
capable of repairing it properly and ensuring it's safety afterwards.

Peter Coghlan.

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