Problem with charge Lenovo LA-H131

[dclass-pro]

Hi guys I have this Lenovo notebook that is driving me crazy:
The customer says he goes into office but when the battery is downloaded all no longer, it has been for the day that we have in Test in the laboratory, I changed 2 new IC Charge batteries and the KBC (I reprogrammed it) and lplying it with a Banch power supply giving 20v to the laptop, start loading, then goes into stop, then after 5 sec. Start again, then stop and then start again and always load.
I cotnrolled the 2 4K resistances on acin and are ok, what do you recommend?

[mon2]

Re: Problem with charge Lenovo LA-H131

Does the laptop work with the adapter?

What is the voltage on the gate pins of the DCin mosfets? Should be ~25v.

[dclass-pro]

Re: Problem with charge Lenovo LA-H131

on pin 30 of the charger I have 25v as soon as I connect the power supply, after 2sec I have 20/21V

[mon2]

Re: Problem with charge Lenovo LA-H131

Often the fault is in the first 2*DCin mosfets.

Remove all power. Meter in resistance mode.

Measure the resistance across each of the DCin mosfets.

So check:

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.

Start with the 2nd DCin mosfet. Often it gets killed first and needs to be replaced.

Since the board works when you bridge the first mosfet, sounds like the 2nd mosfet is leaking.

[dclass-pro]

Re: Problem with charge Lenovo LA-H131

PQ712
Source (1-2-3) & drain (5-6-7-8) 1Mhom
Source (1-2-3) & gate (4) 1.7 Mhom
Gate (4) & drain (5-6-7-8) 10Mhom

PQ740
Source (1-2-3) & drain (5-6-7-8) 3.4Mhom
Source (1-2-3) & gate (4) 5.5 Mhom
Gate (4) & drain (5-6-7-8) 8Mhom

[mon2]

Re: Problem with charge Lenovo LA-H131

Mosfets look to be ok.

What is the voltage to ground of ACOK pin #2 on PU703 (charger IC) ?

[dclass-pro]

Re: Problem with charge Lenovo LA-H131

3,2v

[mon2]

Re: Problem with charge Lenovo LA-H131

The adapter is the proper one to power this laptop ? ACOK is at a good status.

Confirm that resistor PR763 is present and its resistance matches the schematic @ ~4k ohms. No power power in resistance checks.

As a test, remove PQ707 2N7002 mosfet. Power up again and check the voltage on pin #30 of the charger IC.

[dclass-pro]

Re: Problem with charge Lenovo LA-H131

then guys i figured out the problem describing the customer and it really occurs:
If I unplug the battery for 15 sec, when I plug it back in and plug in the power supply, it never charges... NEVER... but that only happens the first time... if I then remove and plug in the power supply then it resumes charging work well. That's why the customer tells me that when it's totally flat the battery doesn't work anymore, it's a really strange problem

[dclass-pro]

Re: Problem with charge Lenovo LA-H131

Now that I can have the problem checked, when it doesn't charge on pin 30 of the charger I always have a fixed 25V

[dclass-pro]

Re: Problem with charge Lenovo LA-H131

The adapter is the proper one to power this laptop ? ACOK is at a good status.

Confirm that resistor PR763 is present and its resistance matches the schematic @ ~4k ohms. No power power in resistance checks.

As a test, remove PQ707 2N7002 mosfet. Power up again and check the voltage on pin #30 of the charger IC.

If I remove PQ707 have always 25V on pin 30

[mon2]

Re: Problem with charge Lenovo LA-H131

Apply the 4k resistor on the gate pins back and test again without the 2n7002 you removed. Leave it off the board.