Teardown: Standard Resistors

[donlisms]

Here's one of the ubiquitous Leeds & Northrup 4000-series resistors;  this one is 10 ohms.  It arrived leaking oil, and the cap was not difficult to unscrew, so I carefully opened it up.

A simplified build order must have been something more or less like:

• Varnish the 30mm brass tube;
• Tie the folded end of the Manganin near the top with (probably) silk thread;
• Wind one layer all the way down, and a second layer part way back up;
• Tie off the end of the winding with silk thread;
• Tie two varnished flat brass strips up along the both sides of the coil;
• Attach one winding end near the bottom of each strip, and a short heavy wire from the terminal near the top;
• Connect those two with (probably) another piece of Manganin;
• More silk thread as necessary;
• Solder those joints;
• Measure, and file the side wires to tune the resistance;
• Measure again, and so on;
• Seal it all up with red paint or shellac or something;
• Fill the can with oil, and tighten it all up.

You can see the 12 little marks where they grabbed the can with some kind of chuck internally at the open end and cut the threads.

The red paint flaked off the silk thread and settled to the bottom of the can.  I will be cleaning all that out and replacing the oil.  I also need to find a sealing method for the lid; it was recommended (at least in the early days) to fasten the lid with shellac; my other resistors really don't want to unscrew.

[donlisms]

More pictures, because... limits!

[donlisms]

And this one... 1 ohm, somewhat historical, from 1930.  This is the earlier earlier model, with a hard rubber top.  It's not exactly as Rosa described, because the hard rubber top does not screw on, it just fits tightly, and the thread extending out the bottom of the central tube screws into a nut soldered onto the inside of the floor of the can, pulling the whole assembly down tight.  Well, more or less tight -- the can is about half full of oil.

No red varnish or paint or whatever, though it's much darker inside than the newer resistors.

This one is two bifilar winds, both wound together in parallel, starting from the same point.  One layer.  The two pairs of winding ends are brought all the way up to the top of the side rails, possibly with a separately-joined piece of Manganin or whatever.  You can see the abrasive tuning on this one, too; it's a bit more aggressive than the 10 ohm resistor.

I like it because it's a little bit historical: baked in 1930, sealed or checked in 1931, nice temperature coefficient (at least as they measured it at the time), and owned by the National Research Council.  I don't think there were all that many of these resistors around at that time.

And this year-long wait after baking is what makes me nervous when you guys put your resistors through some kind of heating adventure, and then wait 15 minutes before measuring!   

[donlisms]

By the way, the 1930's 1 ohm and newer 10 ohm both measure very closely to my best other standards, within a fraction of a milliohm. 

More of the old one ohm:

[Conrad Hoffman]

Can't be sure but the red stuff is usually Glyptal. The stuff goes back a long ways, patented in 1914 and used in paint 1930s. Good properties and I'd never replace it with anything else during a rebuild or spruce-up.

[MegaVolt]

A set of wire-wound!!!!! resistors of 1 GΩ.

[MegaVolt]

Continuation

[bobAk]

Mgsv(мгсв) did not differ in reliability with poor storage.  So it's better to check, perhaps they have changed their characteristics a lot.  Pay attention to the yellow insulators - amber, most likely.

[MegaVolt]

Mgsv(мгсв) did not differ in reliability with poor storage.  So it's better to check, perhaps they have changed their characteristics a lot.  Pay attention to the yellow insulators - amber, most likely.

Yes. This is amber. Lots of amber )

This is a measure of resistance Р4043 (cyrillic)

Resistors are hermetically sealed from thin wire covered with glass. It takes a lot of effort to ruin them. All of them seem correct at first glance. Accurate measurements of 1 GΩ are not so easy


Here are more photos.

[MegaVolt]

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[MegaVolt]

...

[Conrad Hoffman]

I figure a 1 Gohm resistor would have enough wire to circumnavigate the earth!

[MegaVolt]

I figure a 1 Gohm resistor would have enough wire to circumnavigate the earth!

https://ru.wikipedia.org/wiki/%D0%9C%D0%B8%D0%BA%D1%80%D0%BE%D0%BF%D1%80%D0%BE%D0%B2%D0%BE%D0%B4

The thinnest wire has 15 kOhm/m. This is somewhere 67km of wire

[chekhov]

One more decade resistor box - Р4078, 100 Meg/decade

It pretends to be quite hermetic, screws that hold 'legs' are sealed with paint from the internal side.
On the back there is a cap that holds plastic compartment where little pack of silica-gel is stored.

[babysitter]

P4078 - things with faces!

[Nanitamuscen]

A resistive element from the resistance standards produced by the Krasnodar plant of measuring instruments.
It is made of nichrome foil, sintered with a substrate.

[alm]

A resistive element from the resistance standards produced by the Krasnodar plant of measuring instruments.
It is made of nichrome foil, sintered with a substrate.

Thanks for the picture! What kind of resistance standard would contain this element? The only Krasnodar standard resistors I'm finding on Google are the Soviet-era wirewound resistors like P321, but that's probably because I'm not searching in Cyrillic.

[Nanitamuscen]

P3030, P3026 and many others  (р3030, р3026 Cyrillic)

[bsw_m]

The only Krasnodar standard resistors I'm finding on Google are the Soviet-era wirewound resistors like P321, but that's probably because I'm not searching in Cyrillic.

As an example: https://www.ebay.com/itm/334903961471?hash=item4df9d4e77f:g:3YkAAOSwENZd4SpX

[bsw_m]

Microprovod R4033 100MOhm standard:
The standard was purchased in NOS condition.
But it has a problem with the large value of the standard deviation. For this reason, it was disassembled in the hope that the problem was with the additional resistance. But alas, the main resistive element turned out to be problematic here.

Measurement of this standard:
Total number of comparison = 25
Rx value peak to peak = 15.96 ppm
Rx value standard deviation = 4.96 ppm

And the measurement of another good R4033 standard:
Total number of comparison = 25
Rx value peak to peak = 2.76 ppm
Rx value standard deviation = 0.88 ppm

Measurement of problematic main resistive element:
Ambient T = 25.7
Total number of comparison = 15
Rx value peak to peak = 12.65 ppm
Rx value standard deviation = 3.91 ppm
Rx value = 99.86598 MOhm

The main resistive element has  alpha=+2ppm, beta=-0.4ppm and -133kOhm from 100MOhm this data from the paper on it.
The installed potentiometer can adjust the rating within 200 ppm

[0.01C]

ESI SR1050 1M

[0.01C]

[ Specified attachment is not available ]Kelvin-Varley Voltage Divider Model 2891

[0.01C]

Vishay Bridge Module Model 1109

[chekhov]

P3030, P3026 and many others  (р3030, р3026 Cyrillic)

Here is an example of slightly beaten 1R Р3030 resistance standard that was opened for verification

[TimFox]

On your last photo (the resistive element), are any features of the visible pattern used during construction for trimming the value?