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Need help identifying old resistor 1

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rsm7400

Industrial
Mar 6, 2012
52
I have an old resister that blew in a piece of equipment that I need help identifying. It is not like normal resistors that I work with. This is exactly what is written on it:

1.02K
CLARO
RN70B
1021F
CMF 1%

Can someone tell me what I am looking at? I know 1.02kOhms, and I'm guessing 1% tolerance, but I have no idea what the rest of it is or what watt size I need to replace it. Any help is great!

Ryan

________________________________
Ryan M
Quality Engineer
3d Printer Hobbyist
 
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Google the part number, RN70B1021F, and you'll get about four hits. Lots of data.

Looks like "0.500 free air" watt.


 
Seeing as how the old one blew, might it make sense to replace it with a 1 or 2 watt free air rated unit?

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]
 
Thanks for the help, I didnt try searching as one line of text.

________________________________
Ryan M
Quality Engineer
3d Printer Hobbyist
 
Uprating the resistor might just expose the next weak link in the circuit. :)

Still, it's not a bad idea. As long as you have a circuit diagram and parts list for the rest of the circuit.

 
Ok so searching it by "RN70B1021F" brings up 4 results in google but the information has not provided me that much information, I want to find an equivalent resister. I get more information by searching just RN70 but it is still incomplete.

[URL unfurl="true"]https://www.vishay.com/docs/31027/cmfmil.pdf[/url]

using this link I get the it is Mil Style RN70
The "B" is still undefined anywhere that I look
1021 Ohms
F = 1%

Anyone know what the B characteristic is? Or what wattage the equivalent is? I plan on my replacement part being as close as possible. The machine is over 30 years old, has no wiring diagrams, and no manual (it is a custom built machine).

________________________________
Ryan M
Quality Engineer
3d Printer Hobbyist
 
One chart found said .5-1W but now on that previous chart I see that it is likely .75W and the B is just a temperature coefficient ppm, which probably doesnt matter in my application. I appreciate your inputs, and hopefully I will have the tester running by Friday.

________________________________
Ryan M
Quality Engineer
3d Printer Hobbyist
 
It appears that for RN70B..., the B has 'fallen off' the mil spec (MIL-R-10509J) decades ago.

--

"The machine is over 30 years old..."

That explains a few things.

 
More info - more guidance. Got a picture of the resistor and a bunch of the board around it? (Use the camera Image button to include the picture in your post.)

Keith Cress
kcress -
 
Searching for RN70B pulls up suppliers for military components. Given the obsolescence issue with a "over 30 years old" board, is it even worth the calories expended to find an alternative?

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
 
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