Hp 250 g7

[sebulica]

Hi,

I have a hp 250 g7 laptop with a strange issue.If the laptop is off it charges the battery but when i turn it on it "disables" the charger.If the charger is connected and the battery is connected,the charging led will change colour accordingly(orange charging,white fully charged) while the laptop is of.As soon as i press the power button,the charging status led goes off and the laptop starts on battery.The bios,linux or windows will not recognize charger,no matter the charger connected (tried 45,90 and 120w).
If i connect the charger but disconnect the battery,the charging light will turn white and the laptop will not turn on.

I have updated the bios to latest version and the problem persists.I have tried cutting the clk and data pins from BQ24735 and EC but no change overall.

I have measured rails and different voltages and only one things seems odd but not really...If i have the charger and the battery connected and power on the laptop,the second mosfet (PQB12) will have 19v on input from the first mosfet(PQB11) and around 12v(like the battery) on the output.The gate of the second mosfet is controlled by the bq24735...but idk if this is normal or not..

I am at lost for the moment...if someone could suggest anything,i would be grateful.

I have ordered some bq735 but it will take a while until they will arrive.
Also i have attached the schematic.The board model is LA-J951P rev 1.0

[mon2]

Re: Hp 250 g7

Connect a known good hp adapter.

Meter in dc volts mode.

Measure the voltage to ground of ADP_SIGNAL.

Then switch to another power adapter with a different power rating. Measure the voltage to ground again of this signal.

Post each measurement.

[mcplslg123]

Re: Hp 250 g7

DC-In mosfets checked for voltage on pin1-4-8?? Resistance between pins 1-4/1-8/4-8??

[sebulica]

Re: Hp 250 g7

so today,the strangest thing happened....i have tested again with different adapters and measured the ADP_SIGNAL.with the 45w i got 19.73 with 90w i got 19.83 and when i connected the 120w one i got 0....strange.reconnected it and was 19.85 and then the laptop started working again...

now it works just fine with any adapter,battery connected or not.now how do i explain that to the client ?! i did nothing since yesterday when it was dead with any charger.

[mon2]

Re: Hp 250 g7

now how do i explain that to the client?

Alert the client that the positive results may be temporary. Keep an eye for the same fault and to return it to your shop for a deeper investigation, if and when required.

[sebulica]

Re: Hp 250 g7

i don't have a shop...i just fix laptops in my free time and learn from the process.

i have encountered similar behavior with hp before...leaving the board without power for a few hours somehow magically fixes strange issues until someone trips the issue again(bad charger,bad battery,faulty bios battery etc).but still no explanation at least to feel comfortable that i can "fix" stuff like this in the future

anyway thanks for the support