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

[Fr4gz0n3]

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

Thank you very much for the explanation.

So the internal 5V LDO is definitely working because we have +5ALW.

For the PWM part the 3.3v (+3VPCU) is working while the 5V (+5VPCU) is not.

From my understanding the reasons for +5VPCU to be missing are:
- PU4 damaged, does not provide signal to the MOSFETs. This can be. As said I replaced it but it's not brand new.
- PU4 is working but not receives the enable signal. This should not be the case because EN / ON1 is present (5V measured). Does the controller need other signals to activate the switching power supply?
- Faulty MOSFETs. I don't think because were replaced but again are not brand new. I'll take out other two MOSFETs from the donor board and measure them to check they are good and maybe replace PQ49 and PQ54 again.

What's your opinion? What can be checked now?

[mon2]

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

You are one step ahead of me - good stuff.

- PU4 is working but not receives the enable signal. This should not be the case because EN / ON1 is present (5V measured).

So PU4 is being told to turn on both power supplies on this regulator via pins # 14 & 27.

Once the power rail is deemed to be within specs, the power good signal will go logic high.

Confirm it by measuring the voltage of PGOOD1 & PGOOD2.

Why is +5VPCU not working ? It could be many reasons but start with:

1) Meter in resistance mode. Remove all power when measuring in resistance or DIODE mode testing.

Measure the resistance to ground of +5VPCU ? What is the reading ?

If you see 'OL' = over limit -> just select a higher scale on your meter.

A LOW resistance reading is not a good thing and means there is a shorted part on the rail; most likely a bad capacitor.

Post the reading.

2) Confirm the mosfets are good. Still with NO power; Meter in lowest resistance scale on your meter.

Check the resistance of each mosfet @ PQ54 & PQ49 as follows:

SOURCE (1-2-3) & DRAIN (5-6-7-8)
SOURCE (1-2-3) & GATE (4)
GATE (4) & DRAIN (5-6-7-8)


Checking again for a low resistance reading which means the mosfet is defective.

Repeat the testing for both mosfets on this rail.

If the resistance is high then the fault is elsewhere and could be a defective or incorrectly soldered PU4. You can reflux it and reflow the part to allow for the solder contacts to properly settle on the SMD pads. Be patient and do not push too hard with the tweezers to make PU4 'dance'. Be sure the part is able to move, naturally under the heat.

[Fr4gz0n3]

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

Hi problem solved! Now the laptop is working correctly. I reflow the solder joins of the MOSFETs and the controller with the iron. Then the board started to work. So probably the problem was the step down controller damaged by my wrong actions. Maybe also one of the MOSFETs.

Thank you very much for your help and all the informations.

[mon2]

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

Well done!!

[Fr4gz0n3]

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

Thank you for the support