[HECnet] Bringing up a MicroVAX 3100-80

[Dave McGuire]

On 3/27/20 1:21 PM, Fred wrote:
>> There is a big metal cage, which doubles as a heat sink, over the
>> entire board that is soldered to it at several places.
>>
>>  We now have a stack of six that have failed.
> 
> Hmmmmm.  That may have unlocked the mystery of what happened to the one
> I had attached to my 4000/90A that I ended up virtualizing with SIMH. 
> Just went up and died one day and wouldn't power on.  No smoke, no pop,
> just powered itself off one day and wouldn't power back on.  Tested
> everything I could (power cord, plug on the shelf itself, etc).  Short
> of busting it I couldn't figure out how to get "in" to the power supply
> to poke around.
> 
> I kept all of the drives, but scrapped the shelf. :(

  Urr?  Why didn't you just get another power supply?  They are readily
available cheaply, at least for awhile longer.

  The typical failure mode is the "blink blink blink" of the power LED
as the switcher fails to start.  If you open it up, one of the big
output capacitors will have swollen and barfed its guts out onto the board.

> It pained me to
> do that.  I try not to throw *anything* electronic away even if I think
> there is a "whisper" of it being able to be repaired/salvaged for
> parts.  I'm sure everyone on list has got their "bacon" saved by being
> able to rob a part from something that you kept around just in case ...

  Oh yes. :)  And capacitors are a special case anymore; I have a large
(very large) stock of them at my lab.  We draw from that at the museum
on every work day.

               -Dave

-- 
Dave McGuire, AK4HZ
New Kensington, PA