# Old Telephone Exchange Parts



## wicky (Mar 12, 2016)

Anyone know if any palladium in these variable resistors. i think wowen wire is palladium alloy wire. I was to read this a year back on some place that old telephone exchange has palladium wire.

I have a small lot of 1300lb.
includes

Gold and Palladium Points Relays
Rotary Switches(with pure Silver inside)
On/Off Switches
Variable Resistances
Silver plated pins
Tantalum Capacitors
Choppers, Transformers
Large Capacitors
and many other electrical parts soldered/used and packed/New

most interesting are glass tubes like car headlights lamp. is there any PM in those old Tubes
I will keep posting Pictures of Parts and test results for positive identifications










Thanks


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## nickvc (Mar 12, 2016)

From the little I know the points can be PGMs or silver the switches can and frequently do contain values but the simple answer is to test everything before scrapping it. It all looks old tech so the chances are they used lots of values to ensure it worked but where they are ?


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## scrappappy (Mar 12, 2016)

Old telephone systems should have PM's but resistors would not be the place i would start looking for them, especially 50K ohm resistors.


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## wicky (Mar 14, 2016)

scrappappy said:


> Old telephone systems should have PM's but resistors would not be the place i would start looking for them, especially 50K ohm resistors.



Thanks for your reply

You trying to say 'only' 50K ohm resistors have PGMs. What about 20K, 50k variables volume switch? and others like 20k, 100k, 78k resisters


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## scrappappy (Mar 14, 2016)

wicky said:


> scrappappy said:
> 
> 
> > Old telephone systems should have PM's but resistors would not be the place i would start looking for them, especially 50K ohm resistors.
> ...


I wouldn't think to look for PM's in any type of resistor. PM's are used in electronics because they're great conductors of electricity however resistors are used for the opposite reason.. to limit the amount of current going through a connection. You'll likely only find a carbon composition in resistors. Hope this helps


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## g_axelsson (Mar 14, 2016)

When in doubt, break it apart. If the resistive element is a black surface then it's made from cermet, a carbon mixture. No PM:s in that.

If it is a wire like in your first picture it *might* be a PGM alloy. I've never seen them in real world, only read a datasheet once.
Take a piece of the wire, dissolve in aqua regia and test the liquid with stannous to see if there is any precious metals in it.

Göran


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## Anonymous (Mar 14, 2016)

Seriously- unless I've completely lost the plot- those really are not the things to be looking for PMs in within telecoms. Out of all the components in the old kit, those would rank the lowest.

Show us the other parts OP? 

Jon


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## vgecas (Mar 27, 2016)

hi,

i have seen variable resistors containing palladium. these were soviet, high accuracy, potentiometers. some had resistive element (wounded wire) containing 70%Pd and the slider contained 30%Pd. fastest way to decide if it contains PGM is to heat it to yellow glow and let it cool. if it contains PGM it will not tarnish.

TO: scrappappy

i believe potentiometer show in the third picture is rated 50 Ohm, not kOhm. i think so, because it is made in England ant they use comma (,) as a decimal mark, not as a thousand separator. and the three zeros after the comma (,000) shows accuracy level.


P.S. sorry english is not my main language


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## johnny309 (Apr 11, 2016)

vgecas said:


> hi,
> 
> i have seen variable resistors containing palladium. these were soviet, high accuracy, potentiometers. some had resistive element (wounded wire) containing 70%Pd and the slider contained 30%Pd. fastest way to decide if it contains PGM is to heat it to yellow glow and let it cool. if it contains PGM it will not tarnish.
> 
> ...




It has 50Kohms....... and the main value in that is as a working part..... at least they have Ag inside(the connection between the resistor area..carbon....and the leads)


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## wicky (Apr 15, 2016)

Thanks to all for giving inputs on these rheostat/potentiometer/variable resistor.

I been busy in life

I am like blessed to have such a nice place where my hobby, passion and profession is glowing as I keep reading this forum...
Sure I will make my input on exchang's electrical parts and test results by chemicals and XRF also

Thanks again


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