Toshiba L50-A-131 Plugged in, charging but not

[alderick]

Hello everyone,

I have a toshiba laptop who say plugged in charging, but does not charge the battery, I test two differents battery which I know they works on others laptop.

The motherboard is VGFG MB rev2.1
The charging IC is bq24725
I have schematics.

On the charging IC, I measure

pin 1 18,52V
2 18,52
3 19,01
4 19,01
5 3,12
6 2,44
7 0
8 3,24
9 3,19
10 2,32
11 14,84
12 14,95
13 14,96
14 0
15 0
16 5,98
17 14,61
18 14,95
19 14,95
20 18,88


If you have an idea of what can be the problem or what I should check, it would be nice.

Thanks all

[piernov]

Re: Toshiba L50-A-131 Plugged in, charging but not

Shorted DC-in MOSFET.

[alderick]

Re: Toshiba L50-A-131 Plugged in, charging but not

Should I replace both two first MOSFET?

[piernov]

Re: Toshiba L50-A-131 Plugged in, charging but not

The one that's shorted at least. Probably first one.

[alderick]

Re: Toshiba L50-A-131 Plugged in, charging but not

The first one is short, thank you for helping me
I ordered 3 new on ebay, I'll come back when it's done to feedback.

How do you know for the short? by experience? or it's because the voltage on pin4 is suppose to be 6V higher than pin3?

[piernov]

Re: Toshiba L50-A-131 Plugged in, charging but not

By experience because it is somewhat common to happen (especially on Asus although here it's Toshiba), and there are a couple of clues in the measurements too.

Pin 1 ACN and pin 2 ACP have 18.5V on then, which means current sense R8814 receives and outputs 18.5V (no voltage drop across it btw), and Q8801 has 18.5V on its drain as well.
Pin 3 CMSRC has 19.0V on it, meaning that Q8801 has 19.0V on its source.

With that we know there's a 0.5V voltage drop across Q8801. Under normal operating conditions, it should be very close to 0 (to avoid wasting power), which means the current is actually flowing through the body diode (hence the 0.5V voltage drop) rather than through the drain-source junction, so most likely gate signal isn't good, but it also means this MOSFET is most likely not shorted (otherwise there would be 0V drop across it).

And indeed gate signal on pin 4 ACDRV is at 19.0V, when for N-channel MOSFET it should be around 6V higher than source indeed, so it should be around 25V.
In this state Q8800 should not be passing current (because it has 19.0V on its source and 19.0V on its gate, and body diode is in reverse). We also guess that it has 19.0V on drain.
Basically it has 19.0V on all its pins, so it is shorted internally.

[alderick]

Re: Toshiba L50-A-131 Plugged in, charging but not

Thanks for the explanation, I'm waiting for the MOSFET now and come back after replacement.

Have a great day.

[alderick]

Re: Toshiba L50-A-131 Plugged in, charging but not

I received the MOSFET this morning, after replacement, the battery is charging ok.
There is 24.5V on the gate, which is, according what you said, OK.

Thank you so much for the help!

[frica]

Re: Toshiba L50-A-131 Plugged in, charging but not

By experience because it is somewhat common to

And indeed gate signal on pin 4 ACDRV is at 19.0V, when for N-channel MOSFET it should be around 6V higher than source indeed, so it should be around 25V.

¡¡ Fantastic explanation piernov!! Your are wondeful! One question from a no expert:

All the N-channel MOSFET should be around 6V higher than source???

[mcplslg123]

Re: Toshiba L50-A-131 Plugged in, charging but not

Yes, That applies to all N Channel mosfet. Gate voltage should be higher by 6v then source.

[frica]

Re: Toshiba L50-A-131 Plugged in, charging but not

+1 !!

[surecando]

Re: Toshiba L50-A-131 Plugged in, charging but not

That is a great post about N Channel MOSFET - I think this will help me resolve a problem with a laptop that's been sitting for repair for a while. So the Gate should have at least 6V more then the source for a N Channel MOSFET.

[mcplslg123]

Re: Toshiba L50-A-131 Plugged in, charging but not

That is a great post about N Channel MOSFET - I think this will help me resolve a problem with a laptop that's been sitting for repair for a while. So the Gate should have at least 6V more then the source for a N Channel MOSFET.

This is very basic stuff nothing great about it. All P channel mosfet gate voltage will be lower then source eg source=19V, gate=8V. Similarly for N channel, source=19V, Gate=25V.

[Nycu]

Re: Toshiba L50-A-131 Plugged in, charging but not

Hi. I am having kind of a similar problem with Toshiba L50-B-1N9, motherboard DABLIDMB8E0-REV:E.
When I connect the charger, the charging light comes on but the laptop does not react to the power button (Wich I checked and it is ok).
If I connect the motherboard directly to a DC Power Supply, it powers on.
I am new to this so please have patience with me

[Kovacs1122]

Re: Toshiba L50-A-131 Plugged in, charging but not

Hi. I am having kind of a similar problem with Toshiba L50-B-1N9, motherboard DABLIDMB8E0-REV:E.
When I connect the charger, the charging light comes on but the laptop does not react to the power button (Wich I checked and it is ok).
If I connect the motherboard directly to a DC Power Supply, it powers on.
I am new to this so please have patience with me

I know its late but have you tested the same mosfet for internal short ?

[manuel.it.solution]

Re: Toshiba L50-A-131 Plugged in, charging but not

Please test for shorts on board