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I have blown this transistor while probing a GPU card, I usually take as much care as I could to probe a living device, but yeah, it's not the first time.

I have identified the short I caused and it was a shorted transistor (which also shorted or opened another transistor that connects to the base of this transistor from its collector). It is apparently an NPN one based on the research of the marking code, but based on the need of that transistor it seems more of PNP transistor. I searched many places with the marking ADBA and number 2A on the side as shown in the picture, but could not find any definite answer, as AD is the marking and BA is something like year/week or something else. Honestly, I'm no expert.

How do I identify something similar? I already did the SMD code search with the type SOT-23 or SC-70 etc., but with no success. Or maybe I already found what I want but there are many and they all seem to be doing different things, but can still fit the need above to drive a 12 V fan.

enter image description here

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The 2A part would represent a 3906, a BJT PNP. Not sure what the ADBA would be. The 3906 would fit your preliminary analysis.

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  • \$\begingroup\$ Thanks Louis, is the 2A the marking in this case? \$\endgroup\$
    – User9123
    Commented Jan 16, 2022 at 9:27
  • \$\begingroup\$ That is my thinking, Not sure that the ADBA stand for. The 2A marking is standardize for 3906, so if it's not a 3906, why would they indicated 2A. I'm pretty confident. \$\endgroup\$
    – Louis
    Commented Jan 17, 2022 at 4:02
  • \$\begingroup\$ Thanks again, Louis. based on the analysis, it seems to be correct, I will accept your answer, I will also use a PNP BJT with some what higher current rates, as I have seen this transistor explode in several web posts \$\endgroup\$
    – User9123
    Commented Jan 17, 2022 at 8:44
  • \$\begingroup\$ A 4403 would be a good substitute as most parameters are very similar, but can drive 600mA as compare to 200mA for the 3906. Thanks for the vote . \$\endgroup\$
    – Louis
    Commented Jan 17, 2022 at 13:46
  • \$\begingroup\$ Thanks again, Louis, I went with a 2F alternative KST2907A \$\endgroup\$
    – User9123
    Commented Jan 17, 2022 at 20:54

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