Unable to Locate Power Supply Chip on HP Elitebook 840 G3

[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

[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]

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.

[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

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

[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

[mon2]

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

does a beep on the coil means a short... and why is it beeping if I get readings of 5ohms?

Yes, close enough to zero ohms to consider it a short. Do note that some low voltage rails are fine to have a low resistance reading. That is normal for cases like 0v8, 1v0, etc.

L60000 = 173 mv

I would start with this coil as the power rail appears to want to power up but is shutting down to some local event. Review the nearby mosfets and read off their markings. There should be 2 mosfets that will look similar - one for the high side / another for the low side for this switching power supply.

Also any nearby local IC that is likely to be the switching buck converter for that rail. What are the markings of the local IC near L60000? Maybe with enough info, we can locate a common schematic that will show us on how that IC should be wired up for a deeper investigation.

With the resistance reading of 40k ohms on this coil / power rail - the rail is not shorted. This is a good sign.

[Zentech]

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

Yes, close enough to zero ohms to consider it a short. Do note that some low voltage rails are fine to have a low resistance reading. That is normal for cases like 0v8, 1v0, etc.



I would start with this coil as the power rail appears to want to power up but is shutting down to some local event. Review the nearby mosfets and read off their markings. There should be 2 mosfets that will look similar - one for the high side / another for the low side for this switching power supply.

Also any nearby local IC that is likely to be the switching buck converter for that rail. What are the markings of the local IC near L60000? Maybe with enough info, we can locate a common schematic that will show us on how that IC should be wired up for a deeper investigation.

With the resistance reading of 40k ohms on this coil / power rail - the rail is not shorted. This is a good sign.

ok. I made a video, which I think is easier for you to see what I'm doing.
I was able to trace 19V to Q6000 which part of the same Power Supply as L6000. I have 19V coming in but no voltage on gate and of course no voltage on source which I believe is connected to the other mosfet Q60001.
what should I do next? should I check the driver for this mosfet to see why no voltage on gate or try replace mosfet. By the way is this L6000 part of main power rail 19V?
https://youtu.be/e06pz1OEPZc

[Sephir0th]

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

I think we can't continue Like this. I even can't find the Coil L60000 on your Pics, which you mentioned before Just for example.
If there are No Schematics available we need CLEAR Pics of both sides of the whole Board (No zoomed in Pictures). Give the coils Numbers starting from Zero and write them near the coils or write the measured values directly near corresponding coils.
When a suspicious area is found we can continue with zoomed in Pics, but Not yet.

[Zentech]

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

I think we can't continue Like this. I even can't find the Coil L60000 on your Pics, which you mentioned before Just for example.
If there are No Schematics available we need CLEAR Pics of both sides of the whole Board (No zoomed in Pictures). Give the coils Numbers starting from Zero and write them near the coils or write the measured values directly near corresponding coils.
When a suspicious area is found we can continue with zoomed in Pics, but Not yet.

the voltage value for every coil / power supply are above along with their resistance. I also posted pictures. If you zoom in into the pics you can clearly see the coils and numbers. All those voltages are S5 stage (power off with charger connected). L6000 is the first power supply close to the charger. I don't think is for 19V or even if it is suppose to have any voltage at S5 (power off) Because even if it getting 19V on drain, is not going to conduct to source if not polarized on gate (so it is important to know which power supply is providing what voltage and when is it suppose to come on)

[Sephir0th]

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

So you're expecting further Help with this Attitude? Then i have to disappoint you. Without me.

Good luck for solving the issue!

[SMDFlea]

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

Are you using a genuine hp charger.Does the white light come on at the power jack.Have you tried different ram.Have you tested the DC-IN mosfets. Have you found the charger IC and taken voltage and resistance measurements.Have you tried flashing the bios.
Have you made a list of all the voltage regulators you can find on the board,and found schematics and datasheets for those. Is the charger IC and any of the voltage regs the same as in the 840 G2 schematic

[Zentech]

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

So you're expecting further Help with this Attitude? Then i have to disappoint you. Without me.

Good luck for solving the issue!

what attitude?... you just join the forum on 2020. are you looking for newbies to bash?

[SMDFlea]

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

what attitude?... you just join the forum on 2020. are you looking for newbies to bash?

To be fair he did ask you at post #9 for more pictures.Lets not forget,its you who has the board in front of you.If you don`t want to post more pictures thats fine.

[Zentech]

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

I don't see a light when charger is connected. Here are more pictures requested of power supply L6000 (both sides)

[Zentech]

charger IC For HP Elitebook 840 G3

guys, I need to the serial number on an chip on my motherboard. don't have the schematic and chip serial number seems worn out. This is for HP Elitebook 840 G3
Motherboard S/N 6050A2822301-MB-A01
I manage to get the schematic for previous version of laptop, but numbers don't match on the board.
it is U6000, which is near the charger. I took a picture to search for the chip data sheet, but it is not possible to see clearly.

[mon2]

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

That is a very poor quality picture.

Can you pour a bit of alcohol on the top of this IC and use a bright light to read off the laser markings on this device ?

Post all markings on this device, line for line.

2nd line appears to be BQ78 = Texas Instruments but that is not confirmed.

[RethoricalCheese]

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

bq24780s. awful picture but very readable

[Zentech]

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

bq24780s. awful picture but very readable

thanks buddy.. I though it was 747805..
One thing I'm confuse with this board is that in past boards, the charger ic, also provides 3, 5V PVC (REGV) so as soon as you plug in the charger, the ic VREG pin gives you 3, 5V to power on the board. Not in this case... apparently the 3, 5V power supply is separate. How do you find that ic without schematic? VREG is not 3VALW which you can measure at the coil and it is present once the I/O IC starts the board. Some boards are different than other in that sense. How they provide 3.3V and 5V at charger connect (which is not the same as 3, 5VALW)
correct me if I'm wrong
thanks

[mon2]

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

@Zentech,

you are referencing the Richtek charger ICs. They do offer a mix of parts where the +3v3 & +5V0 rails are ALW (always ON) or another version of the same charger IC which will turn ON these same rails via a logic level asserted onto the ENABLE pin.

The versions of the Richtek parts (with and without the ENABLE for the +3v3 & +5v0 LDO rails) are selected by the suffix of the part number. From memory believe that "A/B" versions are ALW where "C" suffix is with an ENABLE pin.

On this TI part, do not see the always on rails.