Re: Looking for a 1998 era Sun VME computer. Photo attached.

Thanks Simon.  Our techs have discussed the fact that electrolytic capacitor 
sometimes dry-out with age, but nobody mentioned a wholesale replacement as a 
fix.  We do have a similar computer which uses the same power supplies which we 
only use for offline testing.  It is a 48 port version of the one which we are 
using online (both made by IMP.)  We lack an extender card, but our techs have 
powered-up the offline computer using one good power supply and probed the 
exposed connectors where another power supply could be installed.  They only 
probed with a DC voltmeter though as you suggested, looking for AC ripple (with 
an oscilloscope I suppose) could have been interesting.  Other users of this 
type of computer have warned us that though the computer runs on 28 VDC, there 
are other signals flowing in the power supply pins which are poorly understood.




----- Original Message ----
From: Simon Fryer <[email protected]>
To: [email protected]
Cc: William Merrill <[email protected]>
Sent: Tue, January 18, 2011 5:25:06 PM
Subject: Re: [Suns-at-Home] Looking for a 1998 era Sun VME computer. Photo 
attached.

Hi,

On 19/01/2011, William Merrill <[email protected]> wrote:
> Thanks Simon and all for your interest in this problem.

This is quite an interesting problem (for me anyway) as it is an
uncommon piece of hardware. It has a certain coolness factor! :)

> I've attached a
> photograph of the computer with part numbers overlaid.  A local expert told
> me
> that the cards are VME (maybe MVME?) but the power connector is not one
> which he
> had seen.  The computer does run on either of the two power supplies (they
> backup each other.)  Technicians here have learned that the power supply
> provides a single voltage, 28 VDC.  The computer is used in our Motorola
> Trunked
> Radio System (Smartzone) controller.  We have removed one of the two power
> supplies and had it repaired with mixed results.

Thanks for the photograph and part numbers. It is really quite informative.

It doesn't look VME to me. I suspect that it is using a backplane with
the same connectors as a VME bus but the cards don't look VME. I don't
know enough about large scale communications systems but I suspect
that the bus is either proprietry to the Motorola Smartzone system or
is a a bus only seen in communications systems.

I did a quick google search for the power supplies and it appears that
you are not the only person looking for replacements. Given the age of
the equipment I suspect that to buy a replacement, it will be
expensive and second hand. Unless of course you know someone who is
scrapping a Smartzone system that you can get for spares.

Looking at the photo and trying to read the text corresponding to the
LEDs, there is battery backup on the supplies as well. This means that
there is some circuitry on the board that is dealing with battery
charging and regulation.

The mixed results repairing is interesting. I guess the techs replaced
a blown semiconductor and returned it to service. Over the years I
have seem some power supplies do some strange when they get older. It
is a pity that you don't have a test rig for the power supply so we
can see the ripple on the supply under load.

A tech with a more practical repair experiance told me of stories of
reliability improvements on equipment by global electrolytic capacitor
replacement. While I can not guarantee 100% that it will solve all
your mixed results problems it is something I would consider.

Worst case, a 28VDC power supply should be quite available. With
enough cluggery it can probably be meshed into the system. A couple of
external UPSs and you will have the same sort of functionality as you
have at the moment... Except it will be really ugly. You probably
don't want to go down that route unless you really have to.

Simon

-- 
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"Well, an engineer is not concerned with the truth; that is left to
philosophers and theologians: the prime concern of an engineer is
the utility of the final product."
Lectures on the Electrical Properties of Materials, L.Solymar, D.Walsh