Unable to Locate Power Supply Chip on HP Elitebook 840 G3

[Zentech]

Re: Unable to Locate Power Supply Chip on HP Elitebook 840 G3

guys, has anyone been able to revise my readings? does a beep on the coil means a short... and why is it beeping if I get readings of 5ohms? Finally, how to find a short on a board this big. Can I inject voltage with a power supply? can I do that at one end of the coil and see what gets hot?
any help appreciated

[Zentech]

Re: Unable to Locate Power Supply Chip on HP Elitebook 840 G3

here are my readings (pictures attached if you zoom in you can see the number for each coil) if not let me know I have pictures with microscope.
L60000 = 40k
L60300 = 177 ohms
L63320 = 5 and BEEPS
L66310 = 5 ohms BEEPS
L60500 = 60 ohms
L60200 = 19k
L60100 = 038.7k
L66010 = 5 ohms BEEPS
L66610 = 15 OHMS (BEEPS)
l60800 = 33 OHMS
l60600 = 25K

L60000 = 173 mv
L60300 = 0
L63320 = 0
L66310 = 0
L60500 = 0
L60200 = 5v
L60100 = 3.3v
L66010 = 0
L66610 = 0
l60800 = 1V
l60600 = 1.8v

[mon2]

Re: Unable to Locate Power Supply Chip on HP Elitebook 840 G3

So basically I'm guessing at this point.

Correct. So will everyone else but start with:

1) take clear and zoomed up pix of the logic board. Use another phone if required but the pix must be clear so we can all review the markings on the parts. Post them here.

2) unplug your power adapter from this logic board -> meter in resistance mode (200 ohms is good). Then locate each and every inductor on the logic board. Often they are the honker grey square shaped parts with 2 large (wide) solder pads - sometimes you can see the magnet wire, sometimes they are shielded and will be solid grey in body.

Red meter on the coil (either side is ok).

Black to ground - locate a metal shield on the logic board.

Post the resistance for each found coil.

3) meter in DC volts mode. Black lead to ground.

Red lead to each coil.

Apply the power adapter.

Post the voltage reading on each found coil.

The above is a start. More help can be supplied once we know the DC-DC buck convertor that is a fancy name for a power supply IC that lowers the input voltage from your power adapter.

Does that work to spec ?

You may find that you have some part that is shorted (from the resistance checks we can have a good idea) - sometimes it is a polarized tantalum cap that is causing an excessive current event from the short -> power supply will shutdown and logic board remains off.

[Zentech]

Re: Unable to Locate Power Supply Chip on HP Elitebook 840 G3

According to the Gdrive schematic, the 3v/5v chip providing 3.3v for power button is (TPS51225), look Google picture. It’s little square chip with 20pins (5 by side).
Sometime, passives components (caps, resistors and coils) are parallel at 2 sides of this chip (for providing 3v and 5v).
We can’t read on the chips on pictures that you shared.

I know that info... the problem is that the diagram is for HP Elitebook 840 G2 and my laptop is G3. One generation after. I have not being able to find this schematic. So basically I'm guessing at this point.

[corrize]

Re: Unable to Locate Power Supply Chip on HP Elitebook 840 G3

According to the Gdrive schematic, the 3v/5v chip providing 3.3v for power button is (TPS51225), look Google picture. It's little square chip with 20pins (5 by side).
Sometime, passives components (caps, resistors and coils) are parallel at 2 sides of this chip (for providing 3v and 5v).
We can't read on the chips on pictures that you shared.

[Zentech]

I have an HP Elitebook 840 G3, which is not powering on. So I follow troubleshooting steps by verifying voltage.
19V are present on the board.
I have 2.3V at power button. I think it should be 3V.
According to the schematic that power should come from power supply
3 and 5V on page 8. (3 VREG OF U6100)
The problem is that I can't find U6100 on the board. I don't have boardview and the schematic is of elitebook 840 G2.
could someone suggest what to do next?
Motherboard SN: 6050A2822301-MB-A01
https://drive.google.com/file/d/1-3X...UJc3n0m5w/view