[time-nuts] [OT] Re: Solartron 7150plus DMM Failure
GandalfG8 at aol.com
GandalfG8 at aol.com
Tue Sep 22 10:44:24 UTC 2009
In a message dated 22/09/2009 11:16:03 GMT Daylight Time,
robert8rpi at yahoo.co.uk writes:
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.
Thanks for the information.
I wasn't thinking it was anything to to do with a MIL spec, pretty sure
these are standard Solartron spec anyway, but just commented on it being
ex-mil as many have come on to the UK market as military surplus.
However, your comments on storage suggest that origin might be more
relevant than I appreciated.
My three units have all been kept warm and dry here but there's no telling
how they might have been stored in the run up to, and following, disposal,
I've seen plenty of previous examples of ex-mil kit that has suffered from
poor storage conditions.
When I have more time I will see if I can rebuild one of the blown filters,
although these are quite nice meters I'm still reluctant to spend around
£90 on replacement mains connectors.
I agree it's the snap in issue that makes it much more awkward but I'm
considering the possibility of fitting an adaptor plate to accomodate a screw
fixing connector/filter, or even an alternative snap in.
Doing away with the voltage selection option is another possibility that
might generate more space to work in.
More information about the time-nuts