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Identifying SOT23 Component
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ChrisGreece52:
Hello i am trying to reverse engineer a PCB but i have a problem identifying an SOT23 component.

Given that SOT23 components usually are diodes or transistors i tried measuring the diode voltages to identify the nature of the component.

In the first ic i got the following results

1(+) --> 2(-) Forward Biased Diode 960mV
1(+) --> 3(-) Forward Biased Diode 960mV
3(+) --> 2(-) Forward Biased Diode 960mV

See problem is the third measurement which if it was an NPN transistor it should be open circuit but it displays a forward voltage of 960mV i do not know if the component is busted or not so that is another problem

There is an identical component above (Markings are 493) and i got the readings below from it.
1(+) --> 2(-) Forward Biased Diode 960mV
1(+) --> 3(-) Forward Biased Diode 960mV
3(+) --> 2(-) Open Circuit
Which tells me that it should be an NPN transistor.

Again i am not sure if both components are operational thank you in advance.
T3sl4co1l:
Is this in circuit or out?

Tim
ChrisGreece52:
Its on the pcb i did not remove it from the circuit. Do you think that is the problem ?
PA0PBZ:
https://www.diodes.com/assets/Datasheets/FMMT493.pdf  :-//
ChrisGreece52:
I found the problem !!! it is not the transistor but that i left it on the board. As i was drawing the schematic i found out that the two transistors are connected together like this.
Where the normal behaving one is the bottom and the one i got the weird measurements from being the top one.
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