HP probook 4510s mosfet issue

[Cuboy]

Hello,

I am currently trying to help a ONG by volunteering to help repair laptops, it's something that i have been into since 2017, always watching videos, on discords, forums etc...

I have an HP ProBook 4510s laptop that does not power on and has no indicator lights, which suggests an issue with the power supply or the motherboard.

I started by verifying that there is voltage at the input of the motherboard, confirming that the power adapter is working correctly. However, when I checked the voltage at the output of the first MOSFET (Q1032), I found 19V at the source and the gate but 0V at the drain, indicating that the MOSFET is not turning on properly.

The issue is that since it's a P-channel mosfet, it should have lower voltage on the gate.

I went on and checked the comparator, U8, this is where the gate get's it's voltage. I found that the output (pin 7) and the supply voltage (pin 8) were at 19V, while the non-inverting input (pin 5) was at 5.11V and the inverting input (pin 6) was at 0.00082V. I also checked the resistance between the output (pin 7) and VCC (pin 8) of the comparator and found it to be 45 kOhms, ruling out a short circuit. The resistance between the output (pin 7) and ground was 60 kOhms, confirming no short to ground.

To further investigate, I desoldered the comparator and measured the resistance between its output and VCC pins, which was 40 MOhms (megaohms), indicating that the comparator itself is likely not the root cause of the issue.

Currently I am on a halt and don't know how to proceed, I would appreciate any help.

[mon2]

Link the schematics or post them in the dedicated schematics forum - not here. Not at my office desk.

check on how this comparator selects when to enable this p-channel mosfet. There may be a resistor based voltage divider that is fed by the raw dc voltage from the power adapter and then this comparator acts like an inverter to pull down the dcin mosfet.

On this note, if the comparator is removed, confirm no will get hurt but ground the gate pin #4 of the first dcin p-channel mosfet while external power is attached. This will enable this p-channel mosfet.

Does the laptop power on?

[Cuboy]

Link the schematics or post them in the dedicated schematics forum - not here. Not at my office desk.

check on how this comparator selects when to enable this p-channel mosfet. There may be a resistor based voltage divider that is fed by the raw dc voltage from the power adapter and then this comparator acts like an inverter to pull down the dcin mosfet.

On this note, if the comparator is removed, confirm no will get hurt but ground the gate pin #4 of the first dcin p-channel mosfet while external power is attached. This will enable this p-channel mosfet.

Does the laptop power on?

Hello thanks for the answer

You're right, the comparator U8 seems to be part of a control circuit that enables or disables the P-channel MOSFET Q1032 based on the input voltage from the power adapter.

Looking at the schematic, there is indeed a voltage divider formed by resistors R130 and R136 connected to the non-inverting input (pin 5) of the comparator.

This is the schematic: https://www.badcaps.net/forum/troubl...510s-schematic

I removed the comparator but soldered it back, should i remove it again?

And no, the laptop is completly dead, it doesn't power on and there are no lights

[mon2]

Thanks for posting the schematics. The logic flow of the enable signal for these DCin mosfets gives me migraines.

Start with reviewing the ADP_PRES signal. What is the voltage to ground. Given that this same signal is fed into the charger IC @ ACDET, we know that only if the adapter is deemed to be suitable, will this signal be @ 2v4 or higher. Respectively, is this signal @ 2v4 or higher? If not, then the comparator @ U1006-A needs a review.

Can you check your reference on the first DCin mosfet? It is not Q1032 in the posted schematic. The first DCin mosfet is Q25 (FDMC6675). Would you agree? It is a P-channel mosfet.

FDMC6675BZ onsemi | Discrete Semiconductor Products | DigiKey

What is the voltage to ground on each pin of Q25 (P-channel) mosfet?

Same review on the mosfet @ Q1018 ? (N-channel mosfet). Need to do our weekly Costco run, will check this thread later after a lighter wallet. Continue to review the DCin path as copied below and be sure the mosfets enable the power path into the ACP / ACN pins of the charger IC. If not, the adapter voltage itself should be reviewed so that the resistor based voltage dividers are reaching or exceeding the threshold set by the comparators. Also, the DCin mosfets may be defective which you can review by checking their resistance with NO power to the board / no battery. Check for low resistance readings. Often, the fault is here - see the sticky above by @Piernov.

[Cuboy]

Thanks for posting the schematics. The logic flow of the enable signal for these DCin mosfets gives me migraines.

Start with reviewing the ADP_PRES signal. What is the voltage to ground. Given that this same signal is fed into the charger IC @ ACDET, we know that only if the adapter is deemed to be suitable, will this signal be @ 2v4 or higher. Respectively, is this signal @ 2v4 or higher? If not, then the comparator @ U1006-A needs a review.

Can you check your reference on the first DCin mosfet? It is not Q1032 in the posted schematic. The first DCin mosfet is Q25 (FDMC6675). Would you agree? It is a P-channel mosfet.

FDMC6675BZ onsemi | Discrete Semiconductor Products | DigiKey

What is the voltage to ground on each pin of Q25 (P-channel) mosfet?

Same review on the mosfet @ Q1018 ? (N-channel mosfet)

I have posted the wrong diagram, i have updated it on the second answer (but yes, q25 is q1032 in this diagram, it's the same but references change, the second one has the same references than my board)

U1-B/ U1006-A :
PIN 5: 0V
PIN 6: 0V
PIN 7 / ADP_PRES: 0.0046V
PIN 8: 0V

For the voltages on q25 (in my board it's q1032, which is the first dcin mosfet)

GATE: 19V
SOURCE: 19V
DRAIN:0V

The Q1018 which on my board and second schematic is Q1033

GATE: 18V
SOURCE: 19V
DRAIN: 19V

It seems that the issue is with the ADP_PRES, since there's no voltage there

[mon2]

Do you have a charged battery on this logic board?

What is the voltage to ground of +VBATR ?

U1, pin # 8 is Vcc (power) pin for this comparator and is fed by the +V5AL rail (+5 volts always). +V5AL is created by U10 (TPS51125; pin # 17) VREG5 LDO rail.

So, +5V5AL = VREG5 should be ON if U10 is receiving the VIN power rail @ pin # 16 = +VBATR.

[Cuboy]

Do you have a charged battery on this logic board?

What is the voltage to ground of +VBATR ?

No, I have removed the battery, i have dissasembled the laptop and have the motherboard out

voltage on +VBATR is 1V but is going down

[mon2]

Remove all power and measure the resistance (meter in resistance scale) to ground of this same +VBATR rail. What is the measurement?

Does the removed battery still have a charge?

[Cuboy]

Remove all power and measure the resistance (meter in resistance scale) to ground of this same +VBATR rail. What is the measurement?

Does the removed battery still have a charge?

Well that's exactly my question, it's strange, but after having the meter connected to ground for a while it dropped to 0V (maybe some coil/capacitor charge?)

resistance is OL

I think the multimeter on voltage mode discharges something and on resistance mode charges that

[mon2]

Can you measure the battery voltage while it is removed from this logic board and on your work table? Measure directly on the free sitting battery itself between the ground and +V pins. Interested to know if you have a voltage still.

We know that the main power rail is not shorted.

[Cuboy]

Can you measure the battery voltage while it is removed from this logic board and on your work table? Measure directly on the free sitting battery itself between the ground and +V pins. Interested to know if you have a voltage still.

We know that the main power rail is not shorted.

I don't have any tool to measure battery voltage, the battery is hstnn-ib89, is it possible to use the multimeter?

I am looking at some videos to see how.

[Cuboy]

Can you measure the battery voltage while it is removed from this logic board and on your work table? Measure directly on the free sitting battery itself between the ground and +V pins. Interested to know if you have a voltage still.

We know that the main power rail is not shorted.

I cannot measure any voltages in the battery, it's 0v but i am not too sure since it's also haven't been used for a long time

[mon2]

Of course. Configure your multimeter to DC volts (20 volts or higher). Red meter probe to the +V pin. Black meter probe to ground on the battery terminal. What is the measurement?

If 0 volts then the battery may be depleted. From tracing the circuit, it appears to me that you need a charged battery to kick start this circuit based on the need for the +V5AL rail. That is the comparator needs to be powered to enable the DCin mosfets. But the power rail for the comparator is from the TPS51125 IC which is fed by the voltage rail @ +VBATR.

This +VBATR is sourced from either the power adapter (after the DCin mosfets are enabled) or the battery pack (which needs to be pre-charged). Wait on other comments but it appears you need a pre-charged battery which should allow this logic board to function and then the power adapter can continue to charge this same battery. Catch-22 design. Will review again after some strong tea.

[Cuboy]

Of course. Configure your multimeter to DC volts (20 volts or higher). Red meter probe to the +V pin. Black meter probe to ground on the battery terminal. What is the measurement?

If 0 volts then the battery may be depleted. From tracing the circuit, it appears to me that you need a charged battery to kick start this circuit based on the need for the +V5AL rail. That is the comparator needs to be powered to enable the DCin mosfets. But the power rail for the comparator is from the TPS51125 IC which is fed by the voltage rail @ +VBATR.

This +VBATR is sourced from either the power adapter (after the DCin mosfets are enabled) or the battery pack (which needs to be pre-charged). Wait on other comments but it appears you need a pre-charged battery which should allow this logic board to function and then the power adapter can continue to charge this same battery. Catch-22 design. Will review again after some strong tea.

Yes, 0V from the battery, i have tried both ways (since i dont have a + and - sign on the battery)

Thanks for your help, i really appreciate it.

[mon2]

If you have access to Amazon, consider to purchase a battery from your region for testing. You can always return it if it is not required. Ideally, hoping that the battery will have a pre-charged value. We have seen this with most of the batteries we have purchased from Amazon. Continue to post your updates as you troubleshoot this unit. We have not yet reviewed if the mosfets are defective or not so you can test their resistance in the meantime.

With no power (which appears to be the default for your board at this time) -> meter in resistance mode -> measure

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

Post each measurement. Check each mosfet in the power path and also the battery side mosfets. Checking for a low resistance which for a mosfet is bad. Should be hundreds of k ohms if ok.

Thanks for your help, i really appreciate it.

You are quite welcome. Kicking the can on some research which needs attention. You can return the favor by putting in a good word for me with 'Tokyo' (Úrsula Corberó) from Money Heist. Perhaps she needs a laptop to be repaired?

[Cuboy]

If you have access to Amazon, consider to purchase a battery from your region for testing. You can always return it if it is not required. Ideally, hoping that the battery will have a pre-charged value. We have seen this with most of the batteries we have purchased from Amazon. Continue to post your updates as you troubleshoot this unit. We have not yet reviewed if the mosfets are defective or not so you can test their resistance in the meantime.

With no power (which appears to be the default for your board at this time) -> meter in resistance mode -> measure

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

Post each measurement. Check each mosfet in the power path and also the battery side mosfets. Checking for a low resistance which for a mosfet is bad. Should be hundreds of k ohms if ok.


You are quite welcome. Kicking the can on some research which needs attention. You can return the favor by putting in a good word for me with 'Tokyo' (Úrsula Corberó) from Money Heist. Perhaps she needs a laptop to be repaired?

Okay mon2 so I have ended with a hipotesis on what could be happening. Tell me what do you think.

Basically, i see that LS_100R should be higher than the VADP voltage in order for the first mosfet to allow voltage to the second mosfet.


This lead me into Q1025 mosfet, while testing it, I see that the gate has 6V, which tells me that Q1025 must be closed (conducting, for a better word). I see that Q1025 source has 0V. drain has around 1v but we're not interested on that.

This leads me to LIMIT_SIGNAL, which is the voltage that is into the source, this is 0V. LIMIT_SIGNAL comes from the adapter, this leads me to think broken adapter and that i got trolled. LIMIT_SIGNAL should be 7V in order for the first mosfet gate to be lower than the source (see https://www.badcaps.net/forum/troubl...-dead-no-power)


Will purchase a new adapter and keep you updated on the operation's success. And about that favor for Tokyo — once this laptop's up and running, I'll let her know who's the tech wizard behind the scenes. Hopefully, the only 'heist' here was the adapter playing hide and seek with the right voltage! Thanks for sticking with me through this electronic mystery, mon2

[Cuboy]

When shorting the mosfet Q1025 gate and drain, i get around 6v for LS_100R which makes the charging light go on for a second which makes me suspect even more from the adapter.

[Cuboy]

And well, I got trolled!

Basically it was a faulty charger, I tried with a charger that i had lying around and it started.
What an embarassment, well, I hope next time it's a really good fault...

I got a message from the bios saying it's faulty, will check that tomorrow.