[volt-nuts] Multimeter input terminal wear

Bob Albert bob91343 at yahoo.com
Sat Dec 13 13:01:23 EST 2014


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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