HP G62-100SL "killed" by myself - No power

[Fr4gz0n3]

Hi everybody, recently I bought for cheap an HP laptop (model HP G62-100SL) to make practice in repairing, just for hobby.

I want to stress, the fact that I'm a newbie to electronic repairing.

As I suspected the problem was simply a GPU that needed a reflow/reballing so nothing interesting. After the reflow the pc started to operate normally again.

There was just a problem, using a DELL 65w AC adapter, the battery charged but the AC adapter was not recognized by Windows and the laptop refused to start without the battery.

Now I guess that probably the reason was the fact that I was not using an original HP adapter, but at that time I was convinced that there was something wrong with the first MOSFETs of the power circuits.

Following a series of very bad actions guided by my ignorance:
- Firstly I confused the MOSFETs of the 5v step down as the power circuit MOSFETs just because they were the nearest to the 19v plug
- Then I obviously measure 6v instead of the 19v I was expecting, so I though that the problem was the second MOSFET not receiving the enable voltage on the gate.
- So I decide to remove the second MOSFET (low side), short the source and the drain and plug the charger. "Unexpectedly" the laptop stopped to work: no power led, nothing.
- Then I remove the short and plugged the AC adapter again.

"Probably" I should have read good guides like the ones that I later found in this forum and also "maybe" took a look at the schematics before doing this mess.

A brief recap of the current state and the tests I've made:
- The MOSFET I shorted is the low side of the 5v step down. 19v in input and nothing after the first or second MOSFET. No voltage on the gates.
- 19v after the current sensing resistor
- No shorts on the main power rail
- Charger IC seems to be powered. I attached few images with all the measures with AC adapter plugged in.
- 3.3v missing on power button
- No AC adapter led
- No shorts on the board and all the fuses seem ok

Board: DA0AX1MB6F0 REV:F
PC specs: Core I3 330M, Radeon 5430

I kindly ask for a hint of what I should check and thank you for anything that can improve my knowledge. I'm here to learn.

[Fr4gz0n3]

Re: HP G62-100SL "killed" by myself - No power

I add the AX1 boardview, meanwhile I checked SuperIO chip VCCs and are all missing.

Some observations on the stepdown chip RT8206 (labelled PU4 on schematics).
- I guess the chip has power because VCC (pin3) is 5v as well as PVCC (pin19)
- VIN (pin6) seems correct because is 19v
- ENLDO (pin4) is high (14v measured) and LDO (pin7) is enabled (5v measured)
- Enable signals of 5v arrive to EN1 (pin14) and EN2 (pin27)
- No tensions for the 5v MOSFETs gate are generated at UGATE1/DH1 (pin15) and LGATE1/DL1 (pin18). Same story for the 3v MOSFETs with no tensions at UGATE2/DH2 (pin26) and LGATE2/DL2 (pin23). So both 5v and 3v lines are missing: 0v measured at resistors PR220 and PR221
- PHASE1/LX1 (pin16) and PHASE2/LX2 (pin25) are both 0v

The fact that power is provided to the stepdown IC along with enable signals and on the other side there are no outputs, suggest me that the IC is dead.
Do you think the same or I'm missing some signals that can activate this chip? Are there other things to check?

[Techtiger]

Re: HP G62-100SL "killed" by myself - No power

After your bad actions may be +3.3V_ALWP is short as you know PWM section Low voltage high in amps if one fet fault you replace all and never power up without fet , left one pad PL9 and see what side is short to GND , if EC VCC AVCC get a higher voltage ! May be bad EC also , no power in PWRBTWN is normal +3V line is down
For ENLDO depending on the platform they have used Zaner Diode 2 R 1k /150k dividers

[Fr4gz0n3]

Re: HP G62-100SL "killed" by myself - No power

Thank you for the reply. I have lifted the coil (PL9) and measured the resistence: on the mosfet side (Pin1) I read 100ohm to GND while on the other side (Pin2) I have open line.

Do you need other measures?

I've forgotten to mention that I put back the MOSFET that I removed.

[mon2]

Re: HP G62-100SL "killed" by myself - No power

100 ohms to ground on the mosfet side is too low. The other pin of the removed coil SMD pad (+3.3V_ALWP) is a good value which confirms there is no shorted cap downstream.

The low-side mosfet @ PQ47 may be shorted. Remove PQ47 off the logic board and then measure the resistance of this device to check if it is shorted.

Meter in 2k scale (or similar).

Check the resistance of:

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

of the removed mosfet. Post the readings. Checking for a low resistance reading that appears to be the case @ 100 ohms to ground. If still this low, this mosfet is defective and must be replaced.

While testing, perform the same test of the high side mosfet @ PQ46.

Post the readings.

[Fr4gz0n3]

Re: HP G62-100SL "killed" by myself - No power

Ok, PQ46 is definitely good: open line for all G, D, S combinations.

PK47 has source(-) to drain(+) resistance of 600ohm and drain(-) to source(+) resistance of 37Kohm. Open line for source-gate and drain-gate.

EDIT: coil to GND resistance for mosfet side is 35 Mohm now (open line I guess). Probably my previous measure on the other side was bad, because I'm measuring 5Kohm (slowly decreasing over time). Probably my probe was not set correctly due to the restricted space.

[mon2]

Re: HP G62-100SL "killed" by myself - No power

PQ46 looks ok.

Your earlier post notes a 100 ohm to ground. Can you confirm this reading again? Where was this measurement taken?

PQ47 may be faulty. Remove it and check again while it is out of circuit. 600 ohms is low.

Perhaps the fault is with the charger IC.

Do not power up with any of these parts removed.

[Fr4gz0n3]

Re: HP G62-100SL "killed" by myself - No power

Sorry I should be more specific.

Measures on MOSFETS has been made out of circuit and the ones on the sides of the coil has been performed without the 2 MOSFETS.

For coil measures I used black probe on a near GND point and positive probe on the pads of the coil.

Do I need to redo the measures with PQ46 inplace?

[mon2]

Re: HP G62-100SL "killed" by myself - No power

Can you clarify the present details of the logic board? Do you have the high side and low side mosfets removed?

This is PQ46 and PQ47, respectively.

Where is 600 ohms to ground? This is a low reading.

Is this on source to drain mosfet PQ47 pads without PQ47 on the board?

[Fr4gz0n3]

Re: HP G62-100SL "killed" by myself - No power

...I have lifted the coil (PL9) and measured the resistence: on the mosfet side (Pin1) I read 100ohm to GND while on the other side (Pin2) I have open line...

Done with all the components on the board and only the coil with a leg lifted (but probably the open line measure was not correct)

..PQ46 is definitely good: open line for all G, D, S combinations.

PK47 has source(-) to drain(+) resistance of 600ohm and drain(-) to source(+) resistance of 37Kohm. Open line for source-gate and drain-gate...

Done on the MOSFETs out of the circuit after desoldering them from the board.

...coil to GND resistance for mosfet side is 35 Mohm now (open line I guess). Probably my previous measure on the other side was bad, because I'm measuring 5Kohm (slowly decreasing over time) #EDIT: instead of open line#. Probably my probe was not set correctly due to the restricted space.

Done on the board without high and low side MOSFETs (PQ46 and PQ47)

...Where is 600 ohms to ground? This is a low reading.

Is this on source to drain mosfet PQ47 pads without PQ47 on the board?

No, 600ohm resistance has been measured on MOSFET (PQ47) outside of the circuit between source and drain.

Sorry if not clear enough, I'm doing my best

[mon2]

Re: HP G62-100SL "killed" by myself - No power

"OL" on the meter = over limit. This is a good sign.

The 600 ohms is of concern.

Recommend to replace PQ47 that is showing this low resistance.

Are you in North America or Europe? AliExpress will have this part but if in a rush, we can find a substitute.

[Fr4gz0n3]

Re: HP G62-100SL "killed" by myself - No power

"OL" on the meter = over limit.

Thank you for the correction

Are you in North America or Europe? AliExpress will have this part but if in a rush, we can find a substitute.

I'm in Italy. No rush at all. It's not my personal laptop, it's just a disposable laptop, victim of my experiments .

I've found a donor board for few euros on ebay. Do you think it's a good idea? In case other components have to be replaced.

[Fr4gz0n3]

Re: HP G62-100SL "killed" by myself - No power

Update: I bought both AON7410 and AON7702, they are gonna arrive in few days. The reason why I bought also a spare AON7410 is because it was very difficult to remove from the board and I'm worried that another heat cycle can be fatal for the MOSFET.

I've also bought the donor board as a plane B in case of major damages on the current board or for IC salvage.

Usually I prefer soldering iron to minimize the heat on component and board but for SMD I have to use hot air rework station. Usually I use chipquik flux and 350c if the component has to be reused and 400c if I just want to remove it.
Do you think it's reasonable? Can you give me an opinion?

[mon2]

Re: HP G62-100SL "killed" by myself - No power

Usually I prefer soldering iron to minimize the heat on component and board but for SMD I have to use hot air rework station. Usually I use chipquik flux and 350c if the component has to be reused and 400c if I just want to remove it.
Do you think it's reasonable? Can you give me an opinion?

I think the settings will vary with your personal experience with your tools. We have the BEST 863 hot air tool and overall, very pleased with it. They can support it with spare parts for servicing, if needed.

We use this tool @ 500-550C to remove and solder on the tiny WLCSP devices of the ISL9239 / ISL9240 on macbooks and other rework. Certainly, start with lower temps and low air pressure and increase each as needed to make the part swim in the liquid solder. We know that we have clone AMTECH flux - the real company has crazy pricing for us in Canada. We danced with Amtech for months to carry their product for resale and internal use but literally was all hot air - led to nothing. The clone stuff from Asia is working out just fine at a fraction of the original costs.

[Fr4gz0n3]

Re: HP G62-100SL "killed" by myself - No power

Thanks for the informations. The 863 seems a good rework station indeed.

Amtech flux is becoming a joke nowadays, it's almost impossible to put your hands on a legit product as the market is flooded with fake ones. Even when sold at high price you are not guaranteed to receive an original product. At this point I'm simply avoiding Amtech flux.

But as you said the "fake" one is almost as good as the original. To be honest I could simply use rosin with IPA but gel flux is just too convenient.

[Fr4gz0n3]

Re: HP G62-100SL "killed" by myself - No power

Today arrived the donor board. I swapped the two MOSFETs (PQ46 and PQ47), I've also replaced the IC PU4. Nothing seems to be changed. Voltages are the same as before and no charger led.

Always voltages (5V and 3.3V) are still missing (measured between the coils and GND).

Now I have also a bench PSU. I provided from 5v to 19v to monitor the current, but the board does not take any current.

It seems that some missing signal prevent the two switching power supply to turn ON.

[Fr4gz0n3]

Re: HP G62-100SL "killed" by myself - No power

Good news! Now the always 3.3v line is working. The problem was that the new step down controller was not soldered correctly. Probably 1 or more pins had bad connection.

To recap the current status:
- 19v main power line works. 19v arrives at the MOSFETs of the different power supplies
- Always 3.3v line is working correctly. 3.3v to the BIOS, the KBC and the power button
- Always 5v line still missing. Measured at coil PL5.
- Still no power consumption from the charger
- Still no charger led (Can it has been burnt? Or is just due to the missing of 5V)

I attach few images. Two reports the components replaced in red and one contains the measurements updated (the changes are highlighted in red). I also rename the stepdown controller labels following the schematics, so now are clearer.

Can it be a good idea to try a 5v injection to check if the rest of the board is working?

[mon2]

Re: HP G62-100SL "killed" by myself - No power

Which 3.3 volt is working?

Is it +3VPCU (created by PU4) ?

Always reference the same labels as used in the schematic as there are numerous power rails that can confuse the review.

Do you have +5VALW?

[Fr4gz0n3]

Re: HP G62-100SL "killed" by myself - No power

I'll try to be more specific in the future

The +3VALWP/+3VPCU is present (3.3v measured on PC302) while the +5VALWP/+5VPCU is missing.

I measured:
+3VALW -> 3.3V
+5VALW -> 5V
+10VALW -> 3.5V
+15VALW -> 7.2V

Can I ask you the difference between ALW and ALWP/PCU?

To be noted that the PU4 has been replace with a used one from the donor board so it's not guaranteed to be 100% working.

I forgot to mention that now I'm using the original HP charger.

Thanks as always

[mon2]

Re: HP G62-100SL "killed" by myself - No power

Each power rail will have its own label = net name in the PCB design world. Personally am not a PCB designer but our PCB cad guy states this all the time when we are designing new products.

Respectively, each power rail will have its own characteristics or specs.

Take for example for this logic board:

+5ALW rail. This rail is created by the internal LDO (low drop out regulator) @ pin # 7 of PU4.

Being a LDO (and not a switching regulator = often called a buck regulator if it takes a HIGH voltage as input -> converts it to a low voltage at the output), we do not expect this rail to be a very high current regulator. LDO regulators are not very efficient and literally 'burn' the high voltage down to a low voltage and this results in heating up of the regulator = PU4 IC.

I would guess this LDO is under 1A max for the +5ALW rail. For this reason, the downstream (consumer) rail will be a light load.

Now, take the +5VPCU rail which is still +5V but is rated @ 8A !! and is a switching regulator so it pulses ON / OFF very quickly to reduce the heat from this task. The catch is that this regulator is NOT always ON, it has an ENABLE pin. The above LDO is ALWAYS ON for light loads.

The +5VPCU is a hefty switching power supply for heavier loads.

The ALWAYS ON must be immediately ON upon receiving laptop power to allow for the basic circuits to be powered. Then the ball gets rolling from here...