Trying to find 3v and 5v regulators without schematics... Could it be this IC?

[mattpd]

I have a board that is missing 3v and 5v standby power. I also have a working board to compare. Board is AMPKB-CT which is from an HP all-in-one, but is basically like a laptop board I think. No schematics to be found.

I have googled every IC part number I can find and none of them are 3v or 5v regulators.

There are a few 20 pin ICs that could be it, but I am not sure. They are grouped together with a coil, cap, and mosfets, so it looks like they may be regulators. See attached picture.

"7A FD" is what is inscribed. On the other board says it says "7A FC" so I think the "FC" and "FD" are not part of the partnumber.

[dellxps15]

Re: Trying to find 3v and 5v regulators without schematics... Could it be this IC?

generally 3.3 and 5 volt is a 24 pin 6x4 and is near 2 little inductor. post whole board picture.

[meritosari]

Re: Trying to find 3v and 5v regulators without schematics... Could it be this IC?

"7A FD" is what is inscribed. On the other board says it says "7A FC" so I think the "FC" and "FD" are not part of the partnumber.

I think you have correct track, its regulator DC/DC for 3.3v/5v

here:

https://cdn.badcaps-static.com/pdfs/...6efd1981b0.pdf

[mattpd]

Re: Trying to find 3v and 5v regulators without schematics... Could it be this IC?

I think you have correct track, its regulator DC/DC for 3.3v/5v

here:

https://cdn.badcaps-static.com/pdfs/...6efd1981b0.pdf

Perfect!

What was your process to locate this part online? Or did you just know already?

[meritosari]

Re: Trying to find 3v and 5v regulators without schematics... Could it be this IC?

No, I didn't know, from what dellxps15 mention above.
- trying to find at aliexpress image of mobo AMPKB-CT
- searching in "Richteck marking information code" document for notebook with word 7A

https://www.badcaps.net/forum/showthread.php?t=39126

[mattpd]

Re: Trying to find 3v and 5v regulators without schematics... Could it be this IC?

No, I didn't know, from what dellxps15 mention above.
- trying to find at aliexpress image of mobo AMPKB-CT
- searching in "Richteck marking information code" document for notebook with word 7A

https://www.badcaps.net/forum/showthread.php?t=39126

Thanks for the good info.

I found 19v VIN on this chip on the good board. No VIN or EN on the bad board.

Without schematics I am kind of lost, but I will try to track down why VIN is missing. I can see 19v on other parts of the bad board. Any idea?

[mattpd]

Re: Trying to find 3v and 5v regulators without schematics... Could it be this IC?

I figured it out.

RT8243 was short to ground on VIN pin and a 2.2ohm resistor next to it was open. Replaced both with parts from the good board and it works.

Thanks again.

[mohamedalepgig]

Re: Trying to find 3v and 5v regulators without schematics... Could it be this IC?

Yes you are right also I think 8a also is 8243a regulator for 3.3 , 5

[alas3376]

Re: Trying to find 3v and 5v regulators without schematics... Could it be this IC?

it's a TPS51219 find its datasheet and check

[xmen9004]

Re: Trying to find 3v and 5v regulators without schematics... Could it be this IC?

thanks for the information

[1fg52]

Re: Trying to find 3v and 5v regulators without schematics... Could it be this IC?

Looks like a common problem. Thanks to this thread i found standby voltages went to zero but in my case short circuit is in one rail and Vin got cut (looks from a burn fuse or some copper got kaput). Can be anything downstream and i don't have a thermal camera.

[1fg52]

Re: Trying to find 3v and 5v regulators without schematics... Could it be this IC?

I forgot to mention I desoldered the 3.3v inductor and jumped Vin from the power brick connector to Vin in RT8243 and got 5 and 3.3v standby voltages.
My only problem now is 3.3v rail shorted to grownd :v