Author Topic: Resistors Used in an LM399 Circuit  (Read 7206 times)

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Offline Chance92Topic starter

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Resistors Used in an LM399 Circuit
« on: August 12, 2022, 12:51:18 pm »
I found a reference circuit in an old Valhalla 4300B micro-ohm meter. I wonder what type of resistors these are? Do they have low temp coefficients?
 
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Online Grandchuck

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Re: Resistors Used in an LM399 Circuit
« Reply #1 on: August 12, 2022, 12:53:58 pm »
I will guess that they are wire wound.
 
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Offline Edwin G. Pettis

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Re: Resistors Used in an LM399 Circuit
« Reply #2 on: August 14, 2022, 03:50:42 am »
That is easy to answer, we made those for Valhalla, back in the early '80s, we went by the name GoldStar Resistors then, we made all of their resistors....note the same yellow cases as Ultrohm Plus uses (when available).  They have the same specs as Ultrohm Plus, TCR of 0±3PPM/°C.  Of course they are precision wire wound resistors.
 
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Offline TiN

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Re: Resistors Used in an LM399 Circuit
« Reply #3 on: August 14, 2022, 04:52:39 am »
Spider webs and strategically tilted LM399, -10 ppms to performance  >:D
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Offline Chance92Topic starter

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Re: Resistors Used in an LM399 Circuit
« Reply #4 on: August 14, 2022, 10:41:30 am »
That is easy to answer, we made those for Valhalla, back in the early '80s, we went by the name GoldStar Resistors then, we made all of their resistors....note the same yellow cases as Ultrohm Plus uses (when available).  They have the same specs as Ultrohm Plus, TCR of 0±3PPM/°C.  Of course they are precision wire wound resistors.

Wow! Thank you for the info. I didn't expect someone from the manufacturer to answer my question. EEVblog is a magical place.
 

Offline Chance92Topic starter

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Re: Resistors Used in an LM399 Circuit
« Reply #5 on: August 14, 2022, 10:47:47 am »
Spider webs and strategically tilted LM399, -10 ppms to performance  >:D

Precisely tilted to counter the uneven uneven air flow :-DD This is better than I expected to be honest, considering there's a cooling fan behind without any dust filter, and 20+ years of usage of course.
 

Offline cellularmitosis

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Re: Resistors Used in an LM399 Circuit
« Reply #6 on: August 15, 2022, 06:35:09 am »
That is easy to answer, we made those for Valhalla, back in the early '80s, we went by the name GoldStar Resistors then ;D, we made all of their resistors....note the same yellow cases as Ultrohm Plus uses (when available).  They have the same specs as Ultrohm Plus, TCR of 0±3PPM/°C.  Of course they are precision wire wound resistors.

Wow! Thank you for the info. I didn't expect someone from the manufacturer to answer my question. EEVblog is a magical place.


FYI he still manufactures them, and they are very affordable, should you happen to get bitten by the volt-but bug  ;D
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Offline bbqws60

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Re: Resistors Used in an LM399 Circuit
« Reply #7 on: July 17, 2023, 08:40:39 am »
Do you have more disassembly pictures? I want to take a look inside, but I can't find the disassembly diagram online
 

Offline Chance92Topic starter

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Re: Resistors Used in an LM399 Circuit
« Reply #8 on: July 17, 2023, 09:38:07 am »
Do you have more disassembly pictures? I want to take a look inside, but I can't find the disassembly diagram online

Sure, will do that in the next few days. If you need schematics, you can find them in the manual.
 

Offline Chance92Topic starter

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Re: Resistors Used in an LM399 Circuit
« Reply #9 on: July 17, 2023, 08:42:49 pm »
Do you have more disassembly pictures? I want to take a look inside, but I can't find the disassembly diagram online

Please see below.
 
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Offline EC8010

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Re: Resistors Used in an LM399 Circuit
« Reply #10 on: July 18, 2023, 08:00:25 am »
That is easy to answer, we made those for Valhalla, back in the early '80s, we went by the name GoldStar Resistors then, we made all of their resistors....note the same yellow cases as Ultrohm Plus uses (when available).  They have the same specs as Ultrohm Plus, TCR of 0±3PPM/°C.  Of course they are precision wire wound resistors.

Perhaps (as you are/were in the business), you can enlighten me on some similar wirewound resistors from the 80s. I have seen pale green resistors 14mm diameter and 18mm long marked LT450/C and 0.002% tolerance (!) in values up to 2M in various bits of kit (Fluke 341A voltage calibrator, a mass spectrometer, and a gas monitor). They're definitely wirewound (shows in the impedance) and the proportions suggest they are multi-layer, which seems inevitable for the larger values. I assume they are enamelled resistance wire (manganin?). Do you know anything about these? Anything at all?
 

Offline Mickle T.

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Re: Resistors Used in an LM399 Circuit
« Reply #11 on: July 18, 2023, 09:56:55 am »
Perhaps (as you are/were in the business), you can enlighten me on some similar wirewound resistors from the 80s. I have seen pale green resistors 14mm diameter and 18mm long marked LT450/C and 0.002% tolerance (!) in values up to 2M in various bits of kit (Fluke 341A voltage calibrator, a mass spectrometer, and a gas monitor). They're definitely wirewound (shows in the impedance) and the proportions suggest they are multi-layer, which seems inevitable for the larger values. I assume they are enamelled resistance wire (manganin?). Do you know anything about these? Anything at all?

These were the resistors of the British Mann Components (later Vishay-Mann).
 
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Offline EC8010

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Re: Resistors Used in an LM399 Circuit
« Reply #12 on: July 18, 2023, 12:02:10 pm »
Thank you so much, Mickle T. That's even more than I had hoped for. A data sheet and a dissected one!
 

Offline Conrad Hoffman

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Re: Resistors Used in an LM399 Circuit
« Reply #13 on: July 18, 2023, 05:09:37 pm »
IMO, the words "wire-wound" and "10M" should never be used in the same sentence.
 

Offline TimFox

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Re: Resistors Used in an LM399 Circuit
« Reply #14 on: July 18, 2023, 05:49:21 pm »
IMO, the words "wire-wound" and "10M" should never be used in the same sentence.

"Never"?  series HR5032N from Precision Resistor Co go up to 10 megohm as special order.
2" long, 2.5 W, 1200 V rating
https://www.precisionresistor.com/skin/reboot/pdf/HRSeriesUltraPrecisionWireWoundResistorPDF.pdf

"Well, hardly ever" -- HMS Pinafore

(If I remember correctly, in the late 1960s Argonne Lab built a custom 100 kV voltage divider from 10 megohm wirewounds from Julie Research Labs, but I couldn't track down a reference to them.  The divider was about the same size as my downstairs half-bathroom.)
« Last Edit: July 18, 2023, 06:55:28 pm by TimFox »
 

Online iMo

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Re: Resistors Used in an LM399 Circuit
« Reply #15 on: July 18, 2023, 07:09:47 pm »
My 10Meg WW resistor..
 

Offline Edwin G. Pettis

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Re: Resistors Used in an LM399 Circuit
« Reply #16 on: July 18, 2023, 07:17:55 pm »
On the contrary, we used to make resistors up to 30Meg but as time and material cost rose it became too expensive for many applications except those that needed the power and stability of precision wire wound resistors.  To date, the largest resistors I have made relatively recently were 3 1/3Meg to repair an ESI 1050  10Meg decade box.  1 Meg are still reasonably cost competitive.  Unless you need a precision repair of resistor decade boxes, transfer standards or equipment, usually lessor resistor types will suffice.
 
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Online Nanitamuscen

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Re: Resistors Used in an LM399 Circuit
« Reply #17 on: July 19, 2023, 03:01:25 am »
Previously, resistors were made from a micro-wire in glass insulation with a resistance much higher. These have a resistance of 100 MOhm and 1GOhm.
 
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Offline EC8010

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Re: Resistors Used in an LM399 Circuit
« Reply #18 on: July 19, 2023, 08:28:49 am »
I'm amazed to see 100M and 1G in wirewound. I first encountered a Mann 2M wirewound resistor as part of the potential divider for sampling the output of a 250VDC supply. When I came to design a replacement instrument, I quickly discovered the reason for the wirewound choice; excess noise. The supply needed to be really low noise, preferably < 10uVpk-pk over a 10s sampling aperture. High frequency noise could be filtered away, but not 1/f noise and that's where the original design's wirewound resistor came in because they produce less excess noise (which is invariably 1/f) than composition or metal film. Not being able to find high value wirewounds, I used a string of ten 1M metal film resistors as my sampling resistor and that worked.

I would be most interested to hear further details from those involved in manufacture of high value wirewounds. What diameter wire? Is surface finish of the wire important? (I'm guessing it is.) If multi-layer, is insulation added between layers to solve the voltage gradient problem at one end?
« Last Edit: July 19, 2023, 08:35:45 am by EC8010 »
 

Offline Conrad Hoffman

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Re: Resistors Used in an LM399 Circuit
« Reply #19 on: July 19, 2023, 01:04:51 pm »
I guess if you need it you need it, but I'm sure glad it isn't me doing the winding. Or buying the very fine wire. No doubt that isn't cheap either.
 

Online Wallace Gasiewicz

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Re: Resistors Used in an LM399 Circuit
« Reply #20 on: July 21, 2023, 03:14:25 am »
I acquired some old wire wound resistors

https://www.eevblog.com/forum/beginners/old-wire-wound-resistors/msg4788734/#msg4788734

402.2K  1/10%
They are NOS and if anyone wants one or two, let me know.They have quite high inductance and that is probably a reason for using them. They probably reduced a lot of low freq noise.
« Last Edit: July 21, 2023, 03:16:34 am by Wallace Gasiewicz »
 

Offline EC8010

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Re: Resistors Used in an LM399 Circuit
« Reply #21 on: July 21, 2023, 04:11:38 pm »
They are NOS and if anyone wants one or two, let me know.They have quite high inductance and that is probably a reason for using them. They probably reduced a lot of low freq noise.
With luck, you have a message.
 

Offline Edwin G. Pettis

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Re: Resistors Used in an LM399 Circuit
« Reply #22 on: July 21, 2023, 07:25:15 pm »
The smallest wire I am aware of, at least in the USA is 0,000,4 diameter in Evanohm.  Most modern resistor wire is coated in polyimide, my spec calls for a minimum 220°C rating, dielectric strength is a minimum of 200V even on the thinnest coating.  There is no inter-layer insulation used, the voltage rating of the resistor depends on how many pi is used in the bobbin and the voltage rating usually has a significant derating in use. Wire sizes smaller than 0,001" diameter have become rather expensive, I have not requested a recent quote but my estimate is approximately $50.841 per 0,4536 Kg, so a typical spool would be somewhere in the $3.500,00-$5.000,00 range.  Needles to say this size of wire is quite difficult to manufacture.

I don't know what gauge of wire the Russians used but it would take about 200,000 feet of 0,000,4" wire to make a 1 G resistor.  A 10 M resistor would be about 2,000 feet.  Yes winding 0,000,4 wire is definitely a strain on the eyeballs and requires a very delicate touch.

I try to stay at or above 0,001" wire to keep away from those heavy charges for smaller wire sizes.
 
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Online bsw_m

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Re: Resistors Used in an LM399 Circuit
« Reply #23 on: July 21, 2023, 09:11:23 pm »
I don't know what gauge of wire the Russians used
I don't have exact information what wire diameter was used in the 1G resistor. But there are assumptions that it is the same as in MRX resistors rated 100MegaOhm and higher - the diameter of the conductive core is 2µm, the diameter of the wire on glass insulation is 13µm

Photo through a metallographic microscope is attached. As well as the look of resistive elements.
Resistors on the last photo
100M 0.05% (in spec, after 33 years of storage)
100M 0.1% (in spec, after 33 years of storage)
300M 0.1% 0.05% (in spec, after 33 years of storage)
all have spec. TC <15ppm/°C, typical about 4-8ppm/°C
« Last Edit: July 23, 2023, 08:18:28 pm by bsw_m »
 
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Offline Edwin G. Pettis

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Re: Resistors Used in an LM399 Circuit
« Reply #24 on: July 22, 2023, 12:13:25 am »
Okay, 13um is about 0,000,5" diameter wire which is about 3.200 ohms/ft, so the 1 G resistor needed even more wire to reach 1G.
0,000,4" diameter wire is 10um diameter wire.  Either way, winding a 100M or 1G wire wound resistor is an accomplishment in itself, I wouldn't try it now, maybe 30 or 40 years ago, laughing.  I'm not too surprised that they have held their tolerance, being glass and on the shelf for 33 years, pretty easy duty.
 
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