help needed to identify sot-23 transistor

There is a search engine for surface mount package markings here, but it is far from complete:

There is a site here with quite a few parts, but I couldn't see A009

Remember that it could be a letter "o" not zero and sometimes the last digit is the date code, not the device type.

Unfortunately, it is very hard to identify these parts from the code they aren't even unique so if you do find one which is marked A009, it may not be the one you want.

Can you work out what it is by looking at the voltages on the three pins? Does it go between the fan and ground or the fan and +ve?

Good luck.

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It may not be a transistor; it is possible to have the whole switcher circuitry in a SOT-23 package. ?PNP????

That's very handy. I think I'll go add every SMT part I buy to that just in case I need to ID them later myself!

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HI,

I meant bi-polar not PNP. The broken park is marked as Q317 on the board. The one near by is marked SS which appears to be a MOSFET tr-or and it is also marked as Q316. So I assume that Q317 is also a tr-or. And seems like it is packed not into the SOT-23 but into the SOT-323 because it is a little bigger then the Q316

I'm attaching a scheme very sketchy one

Honestly speaking it absolutely make no sense to me. So most probably I've interpreted something wrong

What I'm 100% sure is that 12V is applied now onto the fan. Previously

+5.85V were applied on low load and 9.5V on full load.

It looks like a p-channel mosfet transistor to me.

I also thought about it. But then its source leg shall be on +12 and not on the ground.

Yes, its source leg is at +12, not ground, because it couldn't work otherwise. It's a common circuit. The sketch is wrong.

um, seems like i have to disassemble my computer to perform some measuring which is a bit of work. But thanks anyway.

Good idea. If we all did that we may have a chance of identifying these things.

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is another place to look for SMT marking codes. They suggest than an A9 in SOT23 may be a Siliconix SI2309DS, a P-channel mosfet. The Vishay/Siliconix data sheet says the marking is simply A9, but another manufacturer of an equivalent part may be marking them A0009. (That's quite a bit to get on a SOT23, it seems like. Usually the codes are just two or three characters.)

Cheers, Tom

Q316, Q317 etc have absolutely *nothing* to do with part type or function; those are part designators. The manufacturers PC layout and build kit list would have more info, like "Q5 NPN 2N2222A,...R23 5K 20Watt". Even markings *on* a part can be what i call "mouse numbers" meaning "house numbers" which are not related to what they really are. A number of large companies use their own internal coding system and have standard parts marked (by the makers) to their specs.

Seems like you are right! Thanks a lot Tom!