I am try identify one of the manufacturer part number from the board. Can anyone identify the SMD Code and manufacturer part number of the following component? enter image description here Code bPBXD power supply part

wider view of surrounding circuit enter image description here

  • 1
    \$\begingroup\$ No idea about those markings, but from the package and location next to a power connector, my guess is its a linear regulator. If it is, you could measure the voltage and buy something equivalent even if you don't know the exact part. \$\endgroup\$ Commented Nov 29, 2021 at 6:28
  • 1
    \$\begingroup\$ There's an inductor next to it, so that's probably a buck converter. Can you post a wider view of the surrounding circuitry? \$\endgroup\$
    – bobflux
    Commented Nov 29, 2021 at 7:41
  • \$\begingroup\$ @user1850479 I wish to measure the voltage but the parts is burned. The output voltage level might be 3.3V. \$\endgroup\$
    – Lok
    Commented Nov 30, 2021 at 1:47
  • \$\begingroup\$ Vdd on that realtek ic is 3.3v typical so that will be the safe bet. Also see that Test Point labeled TP3V3? \$\endgroup\$
    – Passerby
    Commented Nov 30, 2021 at 2:48
  • \$\begingroup\$ Definitely a DC-DC. Looks like pin 2 is GND. Pin 3 is the switch node (LX). Pin 4 is VIN from the barrel jack. Pin 5 is maybe the feedback node (looks like there is a voltage divider). Not sure about pin 1. Maybe it is an enable or something. \$\endgroup\$
    – user57037
    Commented Nov 30, 2021 at 5:10

1 Answer 1


The better picture shows that it is a Buck converter, while the silkscreen says 3.3v. Further, the output voltage (3.3v) is probably set by the ratio of R3 to R4, so if you measure those resistors you can calculate what the reference voltage is (1.22v?). If you also measured the inductance of that inductor, you could possibly replace it with another buck converter without even knowing what it originally was.

However, before doing that, since you have a barrel jack right there, is there anything else on that 5v rail that would be damaged running at 3.3v? If not, short out the buck IC and feed the barrel back 3.3v. Then see if the chip powers up. If you blew up the Buck converter, there is a chance that whatever it was powering also blew up. No point in repairing a dead power converter if everything else on the board is dead too.

  • \$\begingroup\$ Thank you for your suggestions. The DC-DC is burn due to wrong polarity power source connected to the DC jack (normally inner jack +ve, outer jack -ve polarity). The remaining circuit is fine when powered up with 3.3V. Didn't familiar with this SOT23-5 package Buck converter, normally use DPAK or SOIC8 type. Trying luck to repair while order parts with other. May give best guess for this kind of SOT23-5 Buck converter? \$\endgroup\$
    – Lok
    Commented Nov 30, 2021 at 7:43

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.