Electronics > Beginners

What are those?

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epigramx:


I know the second (at least) is probably burned, but it's weird both have an "1WJ" identification mark.

PS. They are both from an HP Laptop PSU.

kars:
i think they are power resistors probably used as a current shunt to measure the current input/output in the psu

epigramx:

--- Quote from: kars on September 27, 2019, 06:10:40 am ---i think they are power resistors probably used as a current shunt to measure the current input/output in the psu

--- End quote ---
I noticed the PCB has R051 and R051-1 for them which made me think they are resistors (but they didn't look like resistors I know of).
To replace those is there a safe alternative or do I need the exact ones? (e.g. regular resistors)
PS. I'm not sure what the original models of those are to begin with.

TomS_:

--- Quote from: epigramx on September 27, 2019, 06:13:48 am ---Resistors to measure current? I don't get that.

--- End quote ---
You can measure the voltage across a resistor of a known value to determine the current flowing through it.

Warhawk:

--- Quote from: epigramx on September 27, 2019, 06:13:48 am ---
--- Quote from: kars on September 27, 2019, 06:10:40 am ---i think they are power resistors probably used as a current shunt to measure the current input/output in the psu

--- End quote ---
I noticed the PCB has R051 and R051-1 for them which made me think they are resistors (but they didn't look like resistors I know of).
To replace those is there a safe alternative or do I need the exact ones? (e.g. regular resistors, and I'm not sure what the original models of those are to begin with)

--- End quote ---

These are typically low-value resistors. Current through the resistor creates a voltage drop across it as per Ohm's law. A followup circuitry then treats the voltage drop as a current information.

https://www.powerelectronictips.com/measuring-current-shunt-resistors/

The magic google formula would be "shunt based current measurements".

Such resistors are also known as "shunts".

If I read this correctly, the A sample is 0.22 ohm (220mOhm) and the B sample is 0.13ohm (130mOhm).

You shall replace them with the same power rating (they can get hot).

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