On 2012-08-13 17:03:50 +0200, "Gareth Magennis"
said:

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.

can be a voltagedetector :
http://www.dz863.com/datasheet-86018...tage-Detector/

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