A beginner in electronics, I have gone into an attempt in fixing an LCD screen (Lacie 324i) that wasn't switching on. I have found that it was due to a small capacitor that was dead at the level of the power circuit. I replaced it and the screen quickly turned back on. Only, a big problem: the whole bottom half of the screen is purple-ish. I took it apart and realised that I had damaged a component (smd) on the circuit at the top of the lcd matrix. The problem is that I have no clue what it is because the code numbers don't correspond to anything that I can identify. I'm posting here a picture on which I have circled in red where the torn component was. Only the soldered leads are left but it was identical to the one just next to it on the right. It measures about 4mm long and 2mm wide. It's written on top of it: B1 and below YO34. Could someone tell me what's the issue and how to find out the value of this component in order to replace by an identical one? Up until now I have just been able to identify that it's a B1-sot89-type but that's all, but maybe I'm mistaken? Any help is welcome! Thank you. enter image description here

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Update : Thanx for your advice. I just realized that there is the same component at the opposite side of the chip card (see picture below), maybe that could help identify what it is ? Any ideas as to the procedure to identify that component ? enter image description here

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    \$\begingroup\$ That's... some really severe damage to that chip. Since it has the part designator Q I would assume it's a transistor of some sort but I can't tell you anything beyond that. It may not be the same as the one next to it, if it's part of a complementary pair, though. \$\endgroup\$ – Hearth Feb 4 at 16:28
  • \$\begingroup\$ Perhaps the remains of a voltage regulator? \$\endgroup\$ – CrossRoads Feb 4 at 17:47
  • \$\begingroup\$ @CrossRoads, normally voltage regulators are labeled with Ux designators, not Qx, that's very likely a transistor \$\endgroup\$ – c10yas May 3 at 9:05
  • \$\begingroup\$ @Perlino28, what is the pinout of that component? If you were to power it on and very carefully measure the voltage of each pad, what do you see? Measure AC and DC voltage if you can in case it is a switching component. Measure the same values on the other side for the component that works. I'd venture a guess that that is part of a buck/boost converter used to drive the LED display. How is it connected to the power planes around it, and to the component next to it? \$\endgroup\$ – c10yas May 3 at 9:10

Take a look at AP432YG-13 This is an SOT89 and the MFG calls out a part marking of B1 in the Datasheet. Might be what you are looking for.

  • \$\begingroup\$ Hi Robert and thank you. Yes it could be the chip needed and I looked at your links. The only disturbing thing about it, is that the 2nd part of the code that I have (YO34) does not seem to correspond with what it should be with their codes " Y W X" as it's mentionned on top of page 9 of the Datasheet you sent me. Am I wrong ? \$\endgroup\$ – Perlino28 Feb 5 at 9:28
  • \$\begingroup\$ ... well and the first part of the code (B1) would be incorrect too regarding the way they attribute it. It is supposed to be the year number don't you think ? But since english is not my native language I might be wrong ! \$\endgroup\$ – Perlino28 Feb 5 at 9:33

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