I'm trying to identify a fault on a printed circuit board in a consumer product. So I tried to find a pin-out diagram, specifications, etc. for this surface mount component designated AA3 03:

AA3 03 AA3 03

There are two of them. I imagine they are ~3V voltage regulators for some small krypton light bulbs wired up in series. But I don't know for sure.

Can anyone definitively identify this component, or cross reference the part number with a more common one; so I can hunt for the specs? Thanks.


1 Answer 1


I could be NPN transistor 2SC4942 (datasheet: http://rtellason.com/transdata/2sc4942.pdf), version with hfe=60-120.

The lack of capacitors nearby (at least on this side of the PCB) would support this theory over the voltage regulator one.

Good luck!

  • \$\begingroup\$ There actually is a capacitor relatively close to each. But I notice they're designated Q1001 & Q1004, so you could be right. \$\endgroup\$
    – voices
    Nov 11, 2017 at 7:50
  • \$\begingroup\$ Oh. My bad, I was so focused on the marking that I didn't notice designators... \$\endgroup\$
    – desqa
    Nov 11, 2017 at 9:01
  • \$\begingroup\$ Yeah, me too. What makes you think this is it, though? I mean.. how does AA3 03 lead to 2SC4942? 60-120V seems a bit low for the high voltage part of this circuit but I'll take another look. \$\endgroup\$
    – voices
    Nov 11, 2017 at 9:20
  • \$\begingroup\$ I think I found some seller on Aliexpress that sold IC marked AA2 (same transistor but different hfe) and from that I found the AA3 version. Later I found this site: smdmark.com/en-US/smd-code-AA3.html that specifically mentions this code. If you look on second page of the datasheet i linked, it states that the marking "AA3" is version with hfe "60 to 120". Also, hfe is gain not maximum volatage. This transistor has maximum voltage Vce of 600V so it should be OK for your application. \$\endgroup\$
    – desqa
    Nov 11, 2017 at 9:56

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