I am repairing a HP Elitebook 745 and found that the 3.3V and 5V rails are not working. My idea was to replace the buck converter ICs, but I can't figure out what the part numbers are. The ICs have the following markings:



I figured out that these are Richtek ICs but don't get any further than that...

Here is a picture of the package:

Picture of the Richtek ICs.

Can anyone help me with this?

  • 1
    \$\begingroup\$ Is it too much to ask to crop and rotate images so they are more useful? \$\endgroup\$
    – JYelton
    Aug 29, 2023 at 20:49
  • \$\begingroup\$ Not working does not mean they are broken or needs replacing - something upstream may prevent these from turning on, or there may be a short circuit downstream. \$\endgroup\$
    – Justme
    Aug 29, 2023 at 20:50
  • \$\begingroup\$ Many websites less reputable than this one can be found offering schematics, for free, by punching the model name and “schematics” into google. I did this for you and a very brief survey of the results seems promising. \$\endgroup\$
    – Bryan
    Aug 29, 2023 at 23:02
  • \$\begingroup\$ Are you sure the marking of the left one is 4W= ? As far as I can tell there is no Richtek part with that marking and package. \$\endgroup\$
    – nanash1
    Aug 30, 2023 at 4:47
  • \$\begingroup\$ @Bryan I searched for hours for the schematics, but I can't find them. All websites showing up in google are all the same type of forum where you need to pay to do anything. \$\endgroup\$
    – cpu20
    Aug 30, 2023 at 19:00

1 Answer 1


The one marked 3B= is a Richtek RT7290A buck converter.

enter image description here

There is no Richtek device in a UQFN-16L package with a 4W= marking. However, there is one with 4M=, the Richtek RT7291BGQUF and it's a 5V buck converter. So I think you misread the markings on the left part. It's not clearly readable in the picture, but to me it looks more like 4M.

enter image description here

  • \$\begingroup\$ The marking is indeed 4M=. Thanks a lot for helping me out so quickly! \$\endgroup\$
    – cpu20
    Aug 30, 2023 at 18:57

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