Mystery Vintage Wirewound Voltage / Wattage

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spaceistheplace

spaceistheplace

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Joined 2012
#1
This is a custom value wire wound circa 1974.

I'm not sure if these types can be assessed based upon their size like others?

I'm curious what the general consensus would be of a wattage / voltage rating for this resistor.

My application would require 300V, 1/4W. Against my better judgement I briefly used them in-circuit to test and they seem to be stable, but wanted to see what others thought.

There is a Dale RN65 and a 1 Watt generic metal film for size reference.

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#2
It appears to be a precision resistor. That means designed to maintain its value, perhaps whatever the temperature etc. Or maybe varies in a known predictable way. Not meant for normal circuit uses, although it may be OK for whatever you have in mind. Depending on how it is constructed it could have quite high inductance, which may or may not be an issue.
 
#3
Resistors are often $.17 for vishay metal film 3 W with the voltage rating, $.01 for .5 W. I might use this for a prototype, but before I put the cover on and put it in the corner under the speaker, I'd put something real and fully specified in it. I buy 20 or 25 of various values when I get a box shipped in from newark. Put the baggies in bins by decade for the future. If you use the upper/lower limit selector, you can often get 1% oddball values a little off standard 20% values, or end of roll taped units at a big discount from normal. Shipping is the cost in resistors, so I keep them in stock. I buy $1 at a time quantity to avoid the "handling" charge for little orders.
I didn't find the value/sale game playing at mouser or digikey.
I find vishay, welwyn, multicomp, metal film & SPC wirewounds usually come from countries that don't make the news for big lies on QA paperwork of consumer products.
 
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#4
DF96 said:
It appears to be a precision resistor. That means designed to maintain its value, perhaps whatever the temperature etc. Or maybe varies in a known predictable way. Not meant for normal circuit uses, although it may be OK for whatever you have in mind. Depending on how it is constructed it could have quite high inductance, which may or may not be an issue.
Click to expand...

It is the Precision Resistor Company, Wirewound Type S.

But I suppose it would also qualify as a "Precision Resistor" as it's .5%.

It's quite a high value so inductance would be minimal from what I gather. It's for use in a tube preamplifier. It's size is not an issue for me.

Wattage not so much an issue, but would like to know what my voltage margin likely is if anyone has seen or used these before.
 
#8
spaceistheplace said:
This is a custom value wire wound circa 1974.

I'm not sure if these types can be assessed based upon their size like others?
Click to expand...
Certainly not: according to similar examples, they shouldn't be more than 0.25W


My application would require 300V, 1/4W. Against my better judgement I briefly used them in-circuit to test and they seem to be stable, but wanted to see what others thought.
Click to expand...
0.25W seems safe, but 300V makes me uncomfortable: they are made from scramble-wound enamel-insulated resistive wire, and that wire is incredibly thin, which means the insulating layer is even thinner.


Over the years, I have accumulated a number of similar construction resistors (because they looked funny, custom, and were cheap enough in the seventies) and I left them untouched: their characteristics are pretty horrendous by modern standards: first, most of them managed to drift out of tolerance although it wasn't that narrow (0.25 or 0.5%), and they are good only for purely DC applications: not only do they have a large self-inductance, but the distributed capacitance is huge too, meaning their impedance curve vs frequency is a complete disaster.

The good news is that because of that, they have to sound fantastic.... (remember R. Schekley law of universal compensation? (or something similar))
 

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#14
Elvee said:
Over the years, I have accumulated a number of similar construction resistors (because they looked funny, custom, and were cheap enough in the seventies) and I left them untouched: their characteristics are pretty horrendous by modern standards: first, most of them managed to drift out of tolerance although it wasn't that narrow (0.25 or 0.5%), and they are good only for purely DC applications: not only do they have a large self-inductance, but the distributed capacitance is huge too, meaning their impedance curve vs frequency is a complete disaster.
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Click to expand...


I could not measure any inductance in the 330k value I have.

With my examples their tolerance is better than .1% with a .5% marked tolerance.

Which is not to discount your experience, but to suggest that maybe this is a higher quality example than you may have been most familiar with.

Equally possible is that I am luckier than you ;-)
 
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