Hp Pavilion x360 No Power

[Adept PC Repair]

I had a pavilion x360 come in (14" model).

Dc jack clearly fried and charger would activate short circuit protection once plugged in.

Changed the dc jack, charger now stays active and I get 19v on the board. However, the unit still won't power on and the battery connectors are getting a constant 2v from the charging circuitry.

I've tested the voltage of the battery when disconnected and it's completely dead, 0v.

Does anyone know if this particular model relies on the battery power in order to power on? Much like a tablet would (doesn't run from direct current from the psu).

Thanks

 

[Porthos]

Does anyone know if this particular model relies on the battery power in order to power on? Much like a tablet would (doesn't run from direct current from the psu).

Doubt it. Bet the board is toast. But that is just a guess since I won't do board level repairs.

 

[coffee]

I had a pavilion x360 come in (14" model).

Dc jack clearly fried and charger would activate short circuit protection once plugged in.

Changed the dc jack, charger now stays active and I get 19v on the board. However, the unit still won't power on and the battery connectors are getting a constant 2v from the charging circuitry.

I've tested the voltage of the battery when disconnected and it's completely dead, 0v.

Does anyone know if this particular model relies on the battery power in order to power on? Much like a tablet would (doesn't run from direct current from the psu).

Thanks

Most likely on that model, The cmos battery is actually the main battery. Therefore its not going to turn on when the battery is dead. The battery should be getting anywhere from 8v to 18v when charging. Just looked at a replacement battery - 12v charging voltage. So, 2v is not going to charge the battery at all. I would not even entertain putting another battery to - even for testing.

The 19v main rail is broken down into smaller voltages usually from a buck converter chip or similar. IC companies are combining more capabilities into single chips so you might find a more advanced buck converter with power management incorporated into it. After the voltage is broke down it goes thru some filtering via a cap and inductor. Then a current limiting resistor. Now, As the battery charges its internal resistance goes up. This starts to limit the current going into the battery. Then when fully charged no current or very little makes it to the battery.

Most likely the battery charge circuit is bad.

First steps to troubleshoot:

If when plugged in (without battery) you see the typical power LED light come on then the 19v rail is fine and also the 3.3v rail is present for startup. Then you should check that you got 5v on the usb port. If that is present then chances are the battery charge circuit is bad. The bios chip should be getting 3.3 volts also. Check that you have 3.3 volts on the power button.

Take the battery and give it 8v - 12v and limit the current to 2A on a external power supply. Let it charge for a few minutes and then plug in only the battery and see if the laptop wakes up. Its not going to take long for the battery to charge up. Just a few minutes or so. As you charge the battery your going to see the current drop off. Thats because resistance is building up in the battery as it charges. This limits current.

Of course, If you do not have a power supply (external bench type) and not motivated to track this down then just put another board in it or trash it

 

[Porthos]

Is this the computer?

 

[Adept PC Repair]

Most likely on that model, The cmos battery is actually the main battery. Therefore its not going to turn on when the battery is dead. The battery should be getting anywhere from 8v to 18v when charging. Just looked at a replacement battery - 12v charging voltage. So, 2v is not going to charge the battery at all. I would not even entertain putting another battery to - even for testing.

The 19v main rail is broken down into smaller voltages usually from a buck converter chip or similar. IC companies are combining more capabilities into single chips so you might find a more advanced buck converter with power management incorporated into it. After the voltage is broke down it goes thru some filtering via a cap and inductor. Then a current limiting resistor. Now, As the battery charges its internal resistance goes up. This starts to limit the current going into the battery. Then when fully charged no current or very little makes it to the battery.

Most likely the battery charge circuit is bad.

First steps to troubleshoot:

If when plugged in (without battery) you see the typical power LED light come on then the 19v rail is fine and also the 3.3v rail is present for startup. Then you should check that you got 5v on the usb port. If that is present then chances are the battery charge circuit is bad. The bios chip should be getting 3.3 volts also. Check that you have 3.3 volts on the power button.

Take the battery and give it 8v - 12v and limit the current to 2A on a external power supply. Let it charge for a few minutes and then plug in only the battery and see if the laptop wakes up. Its not going to take long for the battery to charge up. Just a few minutes or so. As you charge the battery your going to see the current drop off. Thats because resistance is building up in the battery as it charges. This limits current.

Of course, If you do not have a power supply (external bench type) and not motivated to track this down then just put another board in it or trash it

Thank you for your very in-depth reply.

I had a brain wave last night, remembered I had a universal psu without short circuit protection which I had used in the past to find shorts.

Plugged it in and immediately a chip on the other side started glowing red and caught fire.

I don't think there's any coming back from that as the board is charred from the burn.

Removed the chip in question and still a short somewhere else. I'm going to tell the customer it's a replacement board or nothing. At least I got to the bottom of it.

 

[coffee]

Thank you for your very in-depth reply.

I had a brain wave last night, remembered I had a universal psu without short circuit protection which I had used in the past to find shorts.

Plugged it in and immediately a chip on the other side started glowing red and caught fire.

I don't think there's any coming back from that as the board is charred from the burn.

Removed the chip in question and still a short somewhere else. I'm going to tell the customer it's a replacement board or nothing. At least I got to the bottom of it.

Sorry to hear that.

Did you give the 3.3 v rail 19v?

:0

 

[Adept PC Repair]

Sorry to hear that.

Did you give the 3.3 v rail 19v?

:0

Nope, 19v went in through the dc jack.