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What is this SMD component?

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TV-Engineer

New Member
Hello all,

Maybe someone could help identify a component for me?

It's from a laptop's charger board. There are two on there, both on the 19V input line, one straight after the 19V comes to the board, so the rest of the board is fed through this part. The other has a similar function on the other end of the board, where the charging circuitry is. They are designated RS1 and RS2. The second pic shows more of the board to give an idea on size and perspective of the part.

They are in plastic packages - the first one on the board had got hot and was bulging and inflated considerably, like a balloon ready to pop. Still read short, though. The one which is pictured and working fine measures just 0.5 ohms on the meter, which is actually 0 ohms, since just connecting the meter probes together gives me 0.5 ohms resistance...

So, that rules them out as resistors, despite the odd marking of 50 m(ohm sign) F. If they're fuses, it didn't go open despite passing enough current to heat it up and melt it, and they're like none I've seen of the SMD variety, and I wouldn't know the rating from the odd markings on them.

Any ideas anyone please?

**broken link removed**

**broken link removed**

Thank you.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
I would presume they are resistors, and clearly marked with their values - 50 milliohms - or 0.05 ohms. Presumably they are used for monitoring the current taken?.
 

Styx

Active Member
and that DPAK solder on on a skew ;)
 

TV-Engineer

New Member
Thank you very much for your reply, they are indeed current-sensing resistors, and that one is 0.05 ohms as you said.

The exact ones can be purchased in the US at www.mouser.com (only $12 shipping to the UK for parts totalling under 4lbs in weight, very quick in getting here - <1 week for me - and the parts are cheap and SMD parts available in quantities of 1 and over for a change) for anyone who needs them. And here is the datasheet showing the identical part to the one in my picture:

**broken link removed**

made by Koa Speer Electronics.

Hope this info helps someone as much as the previous post has helped me. Thanks Nigel, I do appreciate your time and knowledge.

:D
 
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