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Resistor value

andrufg77

May 8, 2020
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Could you tell me the value of this resistor, it is from a 450w PC power source, it is located next to the large capacitor.
 

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(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
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25,510
It looks like there is a winding in both a clockwise and ant-clockwise direction. If that is true, it's not an inductor, and is probably a low value non-inductive resistor.

Red violet silver? gold green
2 7 ? x0.1 0.5% That doesn't make sense.
2 7 x0.01 5% 20ppm/degC

Yeah, I'd go for it being a 0.27Ω 5% 20ppm/degC resistor.

So this particular resistor isn't particularly high tolerance, but is very temperature stable.

This is probably a current sense resistor. These don't just fail. There must have been a significant overload to cause it to happen. Because the whole idea of a current sense resistor in a power supply is (typically) to provide feedback that limits the maximum current, failure points to a fault somewhere else.

Having said that, replace it once and see what happens.

It turns out to be a pretty difficult set of specs to meet. Here is one possible option. Unfortunately it's not as temperature stable, and nor is it non-inductive. The datasheet says that non-inductive versions are available, but unless you're buying bazillions, that may not be an option for you.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
Joined
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Messages
25,510
And here's one that's a little closer. But do you want to spend $100 buying 10 of them? And do you want to wait 16 weeks?

The same resistor as in my last post, but they have 840 in stock (but you have to order a minimum of 5 -- here.
 

andrufg77

May 8, 2020
2
Joined
May 8, 2020
Messages
2
It looks like there is a winding in both a clockwise and ant-clockwise direction. If that is true, it's not an inductor, and is probably a low value non-inductive resistor.

Red violet silver? gold green
2 7 ? x0.1 0.5% That doesn't make sense.
2 7 x0.01 5% 20ppm/degC

Yeah, I'd go for it being a 0.27Ω 5% 20ppm/degC resistor.

So this particular resistor isn't particularly high tolerance, but is very temperature stable.

This is probably a current sense resistor. These don't just fail. There must have been a significant overload to cause it to happen. Because the whole idea of a current sense resistor in a power supply is (typically) to provide feedback that limits the maximum current, failure points to a fault somewhere else.

Having said that, replace it once and see what happens.

It turns out to be a pretty difficult set of specs to meet. Here is one possible option. Unfortunately it's not as temperature stable, and nor is it non-inductive. The datasheet says that non-inductive versions are available, but unless you're buying bazillions, that may not be an option for you.
Thank you so much for that information, i will search for that resistor and replace it
 
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