HP14 - DA0G7GMB8F0 REV.F

[Darren Hibbert]

Hi.

I bought a HP 14-1629na laptop that had a fault. I'm learning how to fix boards and know the basics but can someone help me out?

Power supply is fine (19v)
Pressing the power button, the power lights for about 2 seconds then goes off and it keeps doing it in a loop until I unplug it.

I opened laptop and can't find any damage. Put my multimeter in buzzer mode and touched a group of 3 inductors and they all buzzed. Checked inductors over the rest of the board and no buzz. Does this mean I have a short circuit?

I used my bench power supply and injected 1v into one of the buzzing inductors and it's pulling 400ma but my Thermal Camera is not picking up any heat spots anywhere on the board. What should I do next?

Please go easy on me as I'm new to this 🙏

[Darren Hibbert]

Anybody?

[mon2]

Unable to locate a schematic for this unit so you will have to be our eyes. Locate the DC in power connector and share pics of the region. Nearby should be 2 x DCin mosfets + charger IC (perhaps the BQ series). Post the top side markings for the DCin mosfets and the battery charger IC.

We need to review against public schematics the operation of the battery charger IC. Then, with no power to the board, measure the resistance to ground of the main power rail. Checking for a low resistance of the main power rail which indicates a shorted component causing an excessive current draw to power down the board.

[Darren Hibbert]

Thank you for your help.

Here is a picture.

[Darren Hibbert]

Battery is charging. Its pulling 2.6amp

[Darren Hibbert]

Just to add, the BIOS chip has no 3.3v

[mon2]

Remove all power. Measure the resistance to ground on the missing 3v3 rail. Checking if there is a short / excessive load on the 3v3 rail.

Also, hunt around for a square IC near the battery connector (may be on the other side of the PCB) and common type is the BQ series.

[Darren Hibbert]

3.3v Inductor is showing 557 ohms.
3.3V on BIOS chip is showing 18K ohms.

5.0v Inductor is showing 40K ohms.

Inductor near battery is showing 12.5v when plugged in and 50K ohms with no power. And it is hot when power is applied (I'm thinking that is normal?)

No BQ chips found but found 2x QA3112 chips.

Other side of board only has an ITE chip and a load of caps.

[Darren Hibbert]

It looks like I'm missing 3v

[Darren Hibbert]

....but if I didn't have 3.3v, surely I'd not be able to power on (blinking powerlight)

[mon2]

The shared pic is not very clear. Unable to read the topside markings of the semiconductors that may be the charger ic. Locate each square IC with pins on each of the sides. Post their topside markings. One of them must be the charger IC. Will be near the battery connector.

If you are missing the 3v3 rail, this may be another nearby ic and will be found by a local inductor with 2 leads. Each power supply is often fitted with an inductor if a switching power supply. Again, you are our eyes on the board. Could not find the schematics for this model.

[mcplslg123]

Most of the newer boards have +3V/5V rail as suspended.That means they will be available only after power on. Give a clear pic of +3V and +5V area.
Dont rush with voltage injection. Its not a kids play and often leads to damage if you dont understand the consequences very well.
Give a clear pic of the 3 inductors which are buzzing. I bet they must be related to CPU vcore and /or VCCGT. These coils are expected to show very low resistance to GND.
Measure the exact resistance to GND on those 3 coils. No power attached,meter set to 200 ohms(and not in diode mode).

[Darren Hibbert]

The shared pic is not very clear. Unable to read the topside markings of the semiconductors that may be the charger ic. Locate each square IC with pins on each of the sides. Post their topside markings. One of them must be the charger IC. Will be near the battery connector.

If you are missing the 3v3 rail, this may be another nearby ic and will be found by a local inductor with 2 leads. Each power supply is often fitted with an inductor if a switching power supply. Again, you are our eyes on the board. Could not find the schematics for this model.

These are the chips near the battery.

[mon2]

ISL9238H is the battery charger.

Datasheet is attached. We can study this datasheet to learn more about how this logic board is working for the same function.

ISL9238_datasheet.pdf

[Darren Hibbert]

Most of the newer boards have +3V/5V rail as suspended.That means they will be available only after power on. Give a clear pic of +3V and +5V area.
Dont rush with voltage injection. Its not a kids play and often leads to damage if you dont understand the consequences very well.
Give a clear pic of the 3 inductors which are buzzing. I bet they must be related to CPU vcore and /or VCCGT. These coils are expected to show very low resistance to GND.
Measure the exact resistance to GND on those 3 coils. No power attached,meter set to 200 ohms(and not in diode mode).

Yes they are close to the CPU.

1 Coil reads - 117 ohms
2nd coil reads - 35 ohms
3rd coil reads - 35 ohms

[Darren Hibbert]

ISL9238H is the battery charger.

Datasheet is attached. We can study this datasheet to learn more about how this logic board is working for the same function.

Ok so not understanding the datasheet much but worked out I should have the main power rail on pin 17, which I do

Pin 17 - (18.3V)
Pin 32 - (13.1V)
Pin 31 - (12.5V)

Battery is charging too.

[mon2]

Are these voltages stable or do they also power cycle every 2 seconds?

[Darren Hibbert]

They power cycle inline with the light on the power button. Hower, Pin 17 always stays at 18.2V even when power cycling.

I also noticed that I cannot stop this power cycle unless I unplug the battery.

[mon2]

Remove all power. Locate pin # 32 (BGATE) on the charger IC. Respectively, once you have the bearing of this pin, search for a nearby mosfet (most likely will be 8 pins with 4 on each side). We need to know the topside markings to find its datasheet. This will be the 'battery mosfet' that enables / disables when the battery is used.

We wish to test if this mosfet is leaking or not by checking its resistance:

source (1-2-3) & drain (5-6-7-8)
source (1-2-3) & gate (4)
gate (4) & drain (5-6-7-8)

No power & no battery to the board during resistance checks. Post each measurement and also the units of resistance (ohms, kohms, etc.). A good working mosfet should be hundreds of kohms for each test.

[Darren Hibbert]

I located pin 32 but now what do I do with it?

Ok so I found a MOSFET just under the battery connector (21321) as shown in picture.

Resistance Source & Drain - 4.5 M ohms
Source & Gate - 0.6 M ohms
Gate & Drain - 11 M ohms.

Second MOSFET nearby is QA3112

Resistance Source & Drain - 41 K ohms
Source & Gate - 2.3 M ohms
Gate & Drain - O.L