Need help to identify a component marked "SF"

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andrewju
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Need help to identify a component marked "SF"

Post by andrewju » Sat Nov 11, 2017 9:46 am

Hi All,

Unfortunately, I wasn't careful enough while taking a cooling fan apart (I just wanted to clean it and replace the bearings...). This is a 4-wires 12V cooling fan with quite a lot of electronics inside. Unfortunately, there are no stickers or markings on the fan itself, so I don't know what model it is. I damaged some component on the PCB, here:

Image

The component I damaged has 4 legs and comes with an "SF" marking on it

Image

It was installed in a hole in the PCB:

Image

(There are no traces or components on the other side of the PCB. And only that "clean" side of the PCB is visible until you take the whole thing apart. It really looked like a plastic latch to me, so I just pushed it - only then to realize I shouldn't have done it...)

Here's the component itself:

Image

It doesn't look like there's a chance to revive it.

Does anyone have ideas on what this thing might be?


P.S. Without this component, the fan jerks once when power is applied, but doesn't start at all.

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jhsa
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Re: Need help to identify a component marked "SF"

Post by jhsa » Sat Nov 11, 2017 10:30 am

I did a little search that came up with this.

http://www.s-manuals.com/smd/sf

It seems there are more components with the same marking. But look at the one from Ricoh which is a voltage regulator..

João

//cloud.tapatalk.com/s/5a06d283e77 ... _ricoh.pdf
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Kilrah
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Re: Need help to identify a component marked "SF"

Post by Kilrah » Sat Nov 11, 2017 11:53 am

Given the placement it is most likely a hall effect sensor to provide RPM reading and/or rotor angle. It's possible it might run without if it's only used to give RPM info to whatever device the fan is connected to.

Note there are burn marks on the top left of your PCB too, and corrosion all over the place.

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Re: Need help to identify a component marked "SF"

Post by andrewju » Sat Nov 11, 2017 12:15 pm

I also thought it's a kind of an RPM sensor. Maybe something like this? Though, the fan doesn't even start without it. :(


P.S. These are not burn marks, this is some flux and a permanent marker (probably a leftover from the factory). I cleaned it with some alcohol, and it all looks fine in that area.

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jhsa
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Re: Need help to identify a component marked "SF"

Post by jhsa » Sat Nov 11, 2017 12:45 pm

Did you check the pdf I have posted? Or can't you see it?

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andrewju
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Re: Need help to identify a component marked "SF"

Post by andrewju » Sat Nov 11, 2017 1:00 pm

Yeah, now I see the pdf! Thanks!

My part looks similar to sot23-4. And that Ricoh looks quite different... I guess it's not that thing.

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Kilrah
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Re: Need help to identify a component marked "SF"

Post by Kilrah » Sat Nov 11, 2017 1:01 pm

Makes no sense to have a voltage reg there, plus all pins are connected to active circuitry while that chip in the PDF has an unused pin.

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jhsa
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Re: Need help to identify a component marked "SF"

Post by jhsa » Sat Nov 11, 2017 1:04 pm

Well I am on my phone, so it is very difficult to see the circuit.. I have made a search for part markings "SF" and that was what came up.. :)
Will have a better look at the pcb when I get to my PC :)

João

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jhsa
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Re: Need help to identify a component marked "SF"

Post by jhsa » Sat Nov 11, 2017 5:12 pm

Guys, it is a hall sensor for sure. Here is the datasheet of the IC it connects to, AM4967..
The HALL connects to pin 9 and 10 of the IC which are hall sensor positive and negative inputs according to the datasheet. Now we just need to find out which part that is..
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jhsa
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Re: Need help to identify a component marked "SF"

Post by jhsa » Sat Nov 11, 2017 5:35 pm

Maybe something like this?

João
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Re: Need help to identify a component marked "SF"

Post by andrewju » Sat Nov 11, 2017 5:56 pm

Gents, you're right!
I just looked at the fan again, and this element is definitely installed in front of rotating magnet. That's why there's a hole in the PCB.

CYSH12AF looks very similar to the one that was installed. In fact, there are lots of similar ones here: www.cy-sensors.com/CY-HallEffectICs.pdf
I'm now reading that document and trying to figure out which one can be the "SF".

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jhsa
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Re: Need help to identify a component marked "SF"

Post by jhsa » Sat Nov 11, 2017 5:56 pm

Here is the last one I could find.. There aren't many around with that pin configuration.. :(

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Re: Need help to identify a component marked "SF"

Post by jhsa » Sat Nov 11, 2017 6:16 pm

I think they all have the same pinout. So, just measure the voltage on Pin 1, and check if pins 3 and 4 are connected to ground. If so, you will only have to order based on the specs, and according to the voltage.. Maybe it will be trial and error.

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Re: Need help to identify a component marked "SF"

Post by andrewju » Sat Nov 11, 2017 6:56 pm

Hmm... With the sensor taken off, there are about 10v on each pad.

None of them is GND - at least not the fan GND.

Image

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jhsa
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Re: Need help to identify a component marked "SF"

Post by jhsa » Sat Nov 11, 2017 7:14 pm

There's a pin (pin 3?) that sems to connect to the emitter of the transistor marked 1P? I believe it is the emitter. Isn't that ground?

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jhsa
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Re: Need help to identify a component marked "SF"

Post by jhsa » Sat Nov 11, 2017 7:51 pm

I have a few questions.. Can you please measure? See picture.
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Re: Need help to identify a component marked "SF"

Post by andrewju » Sat Nov 11, 2017 8:05 pm

João, you're right. I mixed up the wires.
Previous picture is updated with actual voltages.

Yes, the points marked GND on your picture seem to be correct.
Points marked "+V" are 5v.

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jhsa
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Re: Need help to identify a component marked "SF"

Post by jhsa » Sat Nov 11, 2017 8:55 pm

There you go, if you scroll down the IC's datasheet you will find a reference schematics and you see you have the 2 HALL outputs (Pins 2 and 4?) going to pins 9 and 10 of the IC (Hin - and Hin +), and other pin of the HALL (pin 3?) going to ground. And pin 1 of the hall going to +V through a resistor..
This seems to match what we see on the PCB, I would say..
So, it looks like the pinout of the hall effect sensors you found match the PCB..
I believe this should be a switch type of hall effect?
Even if you don't find the original one, perhaps you can get one that works..

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Re: Need help to identify a component marked "SF"

Post by andrewju » Sun Nov 12, 2017 10:42 am

Hugh! I couldn't find ANY of these sensors locally.
Had to order an HW-108A from China...
I will post a (hopefully success) report when it arrives!

Thanks a lot for your help!!! :)

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jhsa
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Re: Need help to identify a component marked "SF"

Post by jhsa » Sun Nov 12, 2017 10:55 am

Yeah, please let us know how it goes :) I bet it is going to work ;)
Good luck.!!

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Re: Need help to identify a component marked "SF"

Post by andrewju » Mon Dec 04, 2017 6:38 pm

I finally got the sensors from China. The fan works again!

Thank you very much!!!

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jhsa
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Re: Need help to identify a component marked "SF"

Post by jhsa » Mon Dec 04, 2017 6:42 pm

Hey good news :) Well done :D

João
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