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SMD transistor ID?

Hi,

trying to ID a 3 terminal SOT 23 device on a PCB. It is marked 2.T I , except the I is not actually an I but an H on its side, so possibly marked

2.T H, dunno.

(I think its SOT23 cos it is just under 3mm wide)

There is one other of these on the PCB, and it measures in circuit like a PNP transistor, i.e. 2 PN junctions at 671mV and 675mV on my Fluke.

There are other similar devices on the PCB marked "JG", "8.S 7(on its side again) and "2.X I".

I have no idea if these markings ID the devices or whether they are just in house markings?

The PCB is from an Akai MIDI controller keyboard, and this SMD device connects to the Anode of the diode connected to the +ve power supply pin of the USB connector. (Presumably for polarity protection) Other parts in this area are a DC input socket and voltage regulator - this keyboard can either be run either using USB power or an external wall wart, so its possibly part of this either/or circuitry.

(BTW, the USB socket had been smashed off the board, taking the inline diode and a small cap with it, and breaking this transistor in 2 pieces. I only noticed this damage after replacing the USB socket!)

Cheers,

Gareth.

Reply to
Gareth Magennis
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can be a voltagedetector :

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Kripton

the ESR Repository @ http://kripton2035.free.fr/esr-repository.html
the Geiger Repository @ http://kripton2035.free.fr/geiger-repositor.html
Reply to
Kripton

2T on SOT23/TO236 is most commonly a surface mount version of 2N4403 - MMBT4403, PMBT4403,SO4403.

Similarly 2X is it's compliment, MMBT4401.

SMD ident lists can be found fairly easily on-line, though none claim to be comprehensive.

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These links will come and go, as they are typically privately maintained by amateurs.

Sometimes these markings are treated just like part numbers on some websites, allowing for simpler searching.

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RL

Reply to
legg

Ah, that's excellent info, I had no idea about any of that - I've never had to up to now.

Thanks,

Gareth.

Reply to
Gareth Magennis

marked

a

had

The odd rotated letters/alien script characters are usually date codes or batch codes or something known only to the maker

Reply to
N_Cook

Fitted a new MMBT4403, and guessed the missing inline diode would be a Schottky - there was a MBRS140 nearby, so fitted one of those.

And it is all now working, so thanks very much again for those links.

Cheers,

Gareth.

Reply to
Gareth Magennis

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