[time-nuts] [OT] Re: Solartron 7150plus DMM Failure
robert8rpi at yahoo.co.uk
Tue Sep 22 10:15:20 UTC 2009
The filter is an FN372 2A unit. This is a common failure. It's due to the particular type of epoxy cased, self-healing capacitor used in the filter. The case encapsulation cracks and if the unit is left in storage damp gets in. The self healing is by the metal coating that forms the capacitor plates vaporising when the insulation breaks down. Evenventually this forms a sort of chain reaction and the whole thing goes up in acrid smoke. It's not related to any MIL spec. The capacitors are used in some Farnell powersupplies and are a common failure there as well. Equipment that is in regular use seems to be OK, leave it in the garage for a year and you may have trouble. The problem with the FN372 is that it's a snap fit and has the voltage selector built in. There is no direct fit alternative that I know of. New FN372's (with better capacitors) are available from RS for under £30.
--- On Tue, 22/9/09, Dave Baxter <dave at uk-ar.co.uk> wrote:
> From: Dave Baxter <dave at uk-ar.co.uk>
> Subject: [time-nuts] [OT] Re: Solartron 7150plus DMM Failure
> To: time-nuts at febo.com
> Date: Tuesday, 22 September, 2009, 9:30 AM
> We had a Marconi 6960 power meter power inlet filter do
> exactly the same
> here a few months ago... As you say, a
> nasty mess... Wasn't a
> Schaffner filter though...
> Just cleanup the mess and replace the filter with a like
> they are all made to a similar
> specification. There are some that are
> NOT rated for UK/EU power line voltages, however they are
> rare, but Ex
> Military? Who knows what the original spec
> was. Check your power line
> voltage too, ours is at 253V most of the time these
> days. The kettle
> boils quickly!
> If you have any concern about the safety of the integrated
> inlet, contact Schaffner themselves, they are not difficult
> to find.
> It's unlikely, but there is a remote chance you may get an
> Start here...
> If you need a replacement, Farnell, CPC, CHS, R&S, etc
> Using an external filter, will compromise any emissions
> filtering, also
> any susceptibility issues too, the (however short) pigtail
> between your
> external filter and the meter, will act as an antenna.
> As for standing equipment on a "Plastic" sheet to prevent a
> mess. Err..
> Fire Hazard?
> How do I know?...
> I work here, it's what we do...
> Dave G0WBX.
> PS: 63A Three Phase power filters make
> more of a mess when they "go
> PPS: On the subject of Ex Military...
> If anyone in the UK has any X Forces kit of any sort,
> clothing to
> vehicles etc. If you wish to leave the UK for any
> reason with it (even
> staying within the EU!) Technically, you now need an
> export licence.
> And it's being enforced by Customs and Excise.
> They are even pulling foreign (EU) nationals at the ports,
> who are
> trying to go back home after a recent ex forces gathering
> in the UK.
> > -----Original Message-----
> > Message: 1
> > Date: Mon, 21 Sep 2009 09:57:51 EDT
> > From: GandalfG8 at aol.com
> > Subject: [time-nuts] Solartron 7150plus DMM Failure
> > To: time-nuts at febo.com,
> Manual_Exchange at yahoogroups.com,
> > test-equipment at mailman.qth.net
> > Message-ID: <c63.500f1240.37e8e05f at aol.com>
> > Content-Type: text/plain; charset="US-ASCII"
> > Hi All
> > Apologies to any who may receive multiple copies of
> this but
> > I thought it worth sending to those lists where
> > previously seen mention of this meter.
> > I have now had two identical failures of Schaffner
> > mains sockets on ex-mil 7150plus DMMs, although
> I'm not
> > suggesting the ex-mil source is particularly
> > In both cases there has been an internal component
> > within the mains socket that caused it to emit
> smoke around
> > the edges of the metal filter cover, accompanied by a
> > goo and a very unpleasant smell.
> > The brown goo is deposited inside the meter in the
> area of
> > the filter, and very messy it is too, with a
> small amount
> > seemingly contained within the smoke and
> splattering on
> > adjacent external surfaces.
> > In neither case did the meter stop working, or even
> pause to
> > cough:-), so I'm assuming it's most likely to be the
> > capacitor directly across the line input that's
> > According to the Schaffner schematic there's no
> varistor in
> > there, which might have been a preferred suspect, but
> > are two series inductors followed by two more
> capcitors, one
> > between each power line and ground.
> > After the failure the meter can continue to be used as
> > stands but really needs a strip down and good
> internal clean
> > in the area of the mains socket, and even then
> it's still
> > likely to smell unpleasant.
> > I don't have time at the moment but will open up the
> > eventually and see what might be done to rebuild or
> just bypass them.
> > Just cleaning the filter internally too would probably
> > reduce the lingering smell.
> > As a general precaution I would suggest, at the very
> > standing these meters on a sheet of plastic and, if
> > anything reasonably close behind it, wall etc,
> folding the
> > plastic up behind it too as extra protection.
> > The unit that failed here today was sitting on the top
> > of a test bench with its back fairly close to the
> wall, the
> > wall is looking better after a good clean but is
> still not
> > very pretty!
> > A longer term fix might be to remove the filter
> > entirely and use an external inline filter if
> > there isn't much spare room inside the unit so I
> don't think
> > an internal stand alone would be an option.
> > regards
> > Nigel
> > GM8PZR
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