[volt-nuts] Multimeter input terminal wear

pa4tim at gmail.com pa4tim at gmail.com
Tue Dec 30 01:55:09 EST 2014


I have over 30 (Multi)meters, active/passive/tubes and a lot of them are analog. Most of them seem to last forever.  From the top of my head I only had to repair 2 analog Philips, a Philips chopper equiped electrometer, a Fluke 845, a Fluke 8020, a Fluke 8000, an Unigor,a huge AVO CT38 and a pocketwatch shaped voltmeter (I think something like 100 years old) A friend just found an old meter for me (Hansen Electric Products, model SC of 5C, could not read that from the pictures) that will need a lot of work. It looks like it was found in a chickenshack)

But only one of them have (maybe) input terminal wear. But on the other hand most are probably not used for many years. The terminals of the AVO CT38 are much to wide (so wide I do not think it is only wear)

Input teminals and bananas have a tolerance. If it was allready at the max new then it can now be to wide. 

The only problem with inputs I have is my IET5000 LCR meter. The input terminals on that meter are to tight, non  of my test leads or stock of new banana's fit, and I have many, many test leads . 


I have a simpson 260 to0, you do not see many of them here. AVO 8 are more common (I have 2 beautifull versions and restored a braille one from a blind friend) I love the resetable overload protection of the AVO 8. It is very fast.

I use an AVO 8 regular for fun. It is in the living room, and supprisingly accurate. I also still use the Fluke 845 and a Philips electrometer. 


I have no experience with selenium rectifiers other then the ones in old 5xx Tek scopes, an old powersupply and a Triumph motorbike, but all still worked. Some old Tek scopes use them. http://w140.com/tekwiki/wiki/Selenium_rectifiers in that wiki they talk about the resistor and modern diode solution.


Fred PA4TIM






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Van: jhummel73
Verzonden: ‎dinsdag‎ ‎30‎ ‎december‎ ‎2014 ‎06‎:‎59
Aan: volt-nuts









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   
> 



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