[volt-nuts] Multimeter input terminal wear

[jhummel73]

Bob Albert via volt-nuts <volt-nuts at ...> writes:

> 
> Funny you should ask about the copper oxide rectifier replacement for the 
Simpson 260.  I can't help you
> much, as the part I used was an original that I had kept over the years 
for just such a need.  I was amazed that
> it was still good, and it definitely fixed the problem.
> I don't know what I might do next time, although I don't use that meter 
much at all.  It does have a 5000 V
> range, something absent from modern units.  It's exceeded by my old 
Triplett 630-NA which has a 6000 V
> range.  My TL-922 Kenwood amplifier runs in excess of 3000 Volts so the 
meters could be useful for
> troubleshooting there.
> For replacing the copper oxide rectifier, I'd suggest germanium diodes 
with resistors selected to match
> the calibration as closely as possible.  It won't be perfect but at least 
will be useful, and for critical
> applications a calibration chart could be made easily.  (I can't see using 
a Simpson 260 for any critical
> application, but what do I know.)
> Bob
> 
>      On Saturday, December 13, 2014 1:25 AM, jhummel73 <jhummel73 <at> 
gmail.com> wrote:
> 
>  
> Bob Albert <bob91343 <at> ...> writes:
> 
> > 
> > I don't think it makes a lot of difference.  I have some meters that are 
> as old as I am and they still work
> > fine.  If there is a problem, it's probably due to poor materials and 
> being careful isn't going to save
> > much life.
> > 
> > In fact, the plugs have springs that also can fatigue.  Often what seems 
> like a jack problem is really a plug
> > problem, and a new plug may fix it.
> > 
> > And finally, there are other things in these units that limit life as 
> well, and there isn't a whole lot you can
> > do about it.  I recently had to replace the copper oxide rectifier in my 
> Simpson 260 in order to get the AC
> > ranges working properly again.  And there is the question whether the 
> switches should be exercised
> > periodically to remove oxide, or if that causes too much wear.
> > 
> > Bob
> > 
> > On Saturday, August 16, 2014 8:33 AM, "Marv  <at>  Home" <marvin.gozum 
> <at> comcast.net> wrote:
> > 
> > I have some >30+ year old devices still in operation and over time, 
> > dirt and less so, oxidation of the contact surfaces, are more 
> > problems than the integrity of the jack's connection by 
> > friction.  Manufacturers and counterfeiter can make very poor jacks, 
> > but the good ones have been trouble free.
> > 
> > When specified, the spec sheet entry for jack 'wear' is called 
> > "mating durability cycles" or variations in those words.  The typical 
> > brand name banana jack is rated to > 10,000 mating cycles, i.e, 
> > connect-disconnect.  Thus, is would imply the less you un/mate it, 
> > the longer it last.
> > 
> > At 06:37 AM 8/16/2014, Andrea Baldoni wrote:
> > >Hello!
> > >
> > >When the multimeter is not in use for some time (say, a day), do you 
> > >think it's
> > >better to leave the banana plugs inserted, or to take them out?
> > >There is a certain wear in plugging and unplugging, but letting 
> > >always in could
> > >enlarge the input jacks as well.
> > >
> > >Best regards,
> > >Andrea Baldoni
> 
> I am wondering Bob, where you got the replacement for the copper oxide 
> rectifier.  I have a bad one too and it seems it be obsolete. Did you use 
> two germanium diodes and trim pots instead?  I have read about this but 
not 
> sure exactly how it is done.
> thanks. JHummel73
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> 
> Thanks Bob, for the reply.  I was curious about the copper oxide rectifier 
because a friend of mine asked me to repair his old Simpson and I discovered 
the rectifier is bad and I wasn't familiar with this type. My friend is 
somewhat of an eccentric fellow and the meter belonged to his uncle who used 
it at GE for many years and he attaches a lot of sentimental value to it.  
He is  not the sort of fellow to dispose of things simply because they are 
old, but I am  thinking to advise to purchase a newer meter. I am just not 
sure how to go about rigging a substitute and then there are the aged 
resistors and old wiring. Also this meter is not fused at all. Safety and 
accuracy a crying out to find a replacement! Though he does seem to exhibit 
a lot of confidence in me that I will be able to repair it...sigh.
Thanks again.
Joe   
>