MSI GT72VR 6RE (MS-1785) - power problem

[danro]

Hello,

I have a MSI GT72VR 6RE (MS-1785) laptop.
Unit work fine on battery only, on AC adapter only and on both together. Also the battery is charging ok.
The problem is: when laptop is work on battery and connect the AC adapter, the unit go off instant. Sometime, but rarely - 1 of 5 adapter connection, not go off. Not matter if unit is in bios or windows.
I was already try with new battery, new AC adapter, new DC jack, but the problem persist. Also write original bios with clean ME and new bios. Unit still go off instant when AC adapter is connected.

Please advise me what else can try or what transient signal must monitorising to find defective component?
I have MS-1782 schematic only, but seems to be similar at least on power part.

Thank you

[mon2]

Re: MSI GT72VR 6RE (MS-1785) - power problem

What is the history of this unit?

If a sudden fault then each mosfet linked to the charger IC needs to be reviewed.

Link or post the schematic here.

Remove all power. Meter in resistance mode.

Check the resistance of the first 2 DCin mosfets.

Source and drain
Source and gate
Gate and drain

Post each measurement and the meter scale used for the measurements.

Repeat for the next DCin mosfet. Finally, repeat for the battery mosfet that is enabled when using only the battery.

Someone is leaking.

[danro]

Re: MSI GT72VR 6RE (MS-1785) - power problem

What is the history of this unit?

If a sudden fault then each mosfet linked to the charger IC needs to be reviewed.

Link or post the schematic here.

Remove all power. Meter in resistance mode.

Check the resistance of the first 2 DCin mosfets.

Source and drain
Source and gate
Gate and drain

Post each measurement and the meter scale used for the measurements.

Repeat for the next DCin mosfet. Finally, repeat for the battery mosfet that is enabled when using only the battery.

Someone is leaking.

Thanks for answer,

Here is the schematic that I use:

https://www.badcaps.net/forum/showthread.php?t=101781

Reading in diode mode, all measurements look ok. I will read also in resistance mode and will post.

[mcplslg123]

Re: MSI GT72VR 6RE (MS-1785) - power problem

Double check resistance on 1st dc-in mosfet. Its likely shorted .Wiser to test out of circuit.

[danro]

Re: MSI GT72VR 6RE (MS-1785) - power problem

What is the history of this unit?

If a sudden fault then each mosfet linked to the charger IC needs to be reviewed.

Link or post the schematic here.

Remove all power. Meter in resistance mode.

Check the resistance of the first 2 DCin mosfets.

Source and drain
Source and gate
Gate and drain

Post each measurement and the meter scale used for the measurements.

Repeat for the next DCin mosfet. Finally, repeat for the battery mosfet that is enabled when using only the battery.

Someone is leaking.

Ok, components arrived few hours ago.

Change both DCin mosfet and that for battery enable when using battery only, but the same situation
When connect AC adapter, the laptop power off, then power on itself (something like reset...)

Unfortunately, I have no idea about the history of this unit. Also is no signs of some before intervention

Any other ideas, please?

Thank you

[mon2]

Re: MSI GT72VR 6RE (MS-1785) - power problem

Does the logic board power cycle on /off / on and repeats when both, the power adapter and battery are connected?

Are you using the recommended power adapter?

[danro]

Re: MSI GT72VR 6RE (MS-1785) - power problem

Does the logic board power cycle on /off / on and repeats when both, the power adapter and battery are connected?

Are you using the recommended power adapter?

ok, to be more specific:

-the unit work fine on battery only
-the unit work fine with AC adapter only
-the unit work fine with battery and AC adapter conected
-the battery is charging ok when AC adapter is connected

if laptop is ON (working on battery only), when connect AC adapter, laptop go OFF, then start again and working fine after that (not power cycle on/off/on...)

yes, is original AC adapter, but already try with 2 others...

thank you

[mon2]

Re: MSI GT72VR 6RE (MS-1785) - power problem

Measure the VCC voltage to the charger IC when it is powered by the battery.

Then review the same when you plug in the power adapter.

Does this pin glitch during the power adapter insertion?

Also watch the ACDRV pin voltage of the DCin mosfets.

When the external adapter is the active power supply, the battery mosfet should be OFF. Measure the voltage on each pin of the battery mosfet when it is only the battery, then again when you attach the adapter.

As a quick test, consider to replace the battery mosfet as this is the gateway between the 2 power supply for the logic board.

On the TI 'BQ' series of charger IC, the REGN is required to have a local cap on this pin. Confirm it.

[danro]

Re: MSI GT72VR 6RE (MS-1785) - power problem

OK, sorry for late, but here latest news.

Was changed: charger IC BQ24780S, both DC IN mosfets, battery mosfet.
Unit work ok from 10 days. Seems that problem solved

Thank you all for help and support!