T40 Battery and charging circuit problem :( *PIC* UNSOLVED!

[asbesto]

Hi all,

I was playing with an external variable power supply trying to turn on my laptop at 15/18 volt ... when trying, I noticed that the power supply I used gave not enough amperes so the laptop start turning "on" and "off" by external power source, while having my battery connected.

I don't know if I can explain in my bad english language: I had my battery on, and the laptop was working. I connected this external power source, and the screen "lighted up" as normally does when I use the external charger. Suddendly, it goes to low light, as it was disconnected - I suppose for a lack of amperes! After a few seconds, it turned on again - and so on for some seconds, up and down

I realized then there was a problem when I heard a strange sound, like a "Fzzzzzz!!" and I turned off this external power supply.

The laptop was working on battery as usual and so I understood that this power unit was not powerful enough.

So I reconnected his original charger, and the screen lighted on as usual.

But now I have a very strange problem!

When I connect or disconnect the power supply, It doesn't make any sound anymore! I remember a "beep beep!" when connecting his charger, and another "beep beep!" when disconnecting; now I have no sound at all!

Also, the problem is with my ACPI applet:

Running on AC, it says battery charging, and it charge at full 100%.

Disconnecting AC ... it says AC power already on! but battery discharges itself as regular ... the problem is : no beep-beep, and also, no "alarms" when battery goes under 2% ... so the laptop shut down without any notice!

Reconnecting the AC, the battery will be charged again!

So it seem that the charging circuitry doesn't recognize the change of state from AC to Battery!

The only way to recognize it is to shut off the laptop, remove the battery and the AC charger, reconnect the battery and reconnect the main charger. After that, I have again the "low battery" alarms, but no "beeps" when turning on the AC charger.



Can someone please help ?

Many thanks, and sorry for my babelfish english language

[richk]

Your English is fine. Simple things first: does your machine make any sound? Is it possible the speakers are muted? (button above keyboard)

[asbesto]

I have working sounds...

Another test I made:

Starting with battery only - laptop turn on as usual - putting the AC charger: BEEP BEEP! as usual ... but then, removing the AC charger does nothing.

It believe to be under AC charger every time!

[frankiepankie]

Never, never, never!! experiment with your ThinkPad with things like other than the original power supply.


You can fry your motherboard.


I think you fried your motherboard charging circuit.

[richk]

Does the icon on the tool bar change when you unplug?

[asbesto]

No, the icon doesn't change.

P.s. I'm using Ubuntu Linux.

Also, I have good electronics skill. So I checked the motherboard.

I found some power FET and a regulator chip. Something tell me that one of those FET is blown out; How I can measure it?

And where I can find a replacement?



The FET's are TPC8109 and TPC8014. The regulator chip is the ADP3806, out of production. The battery got charged so I suppose this ADP chip is working...

Checking application notes in some Toshiba PDF's I see that the TPC8109 is probably used as a switch for the external AC adapter. So, maybe it's faulty!

All fuses are OK, and so seem all little transistors around them...

Any idea about those FETs ? And, where to obtain them?

Thanks!

Moderator note: Please add a warning in the original post when adding inline picture(s) and try to keep the image size to < 50KB, thanks!

[jimmy274]

You should never do this again! I have also good electronics skills, and one thing I do know is not to mess with mobo DC/DC converters - they're made very specific and you cannot experiment with that.
It might be the TPC8109, if you're lucky, but chances are that you've fried something else. Look closely to the area beneath the touchpad - you should see the MAX1631 - controller chip for DC/DC converter on-board. This controller does the drop-out control, so your problem might have something to do with it.
South of MAX1631 there are 2 more MOSFET switches. You should check them as well.
Checking... Well, the best way is to pull them out with hot air, make a simple circuit and apply the voltage to the gate - see if the source (drain) current is rising as you raise the voltage from Gnd (NMOS), or lower it from Vdd (PMOS). The other, less informative way is to put a multimeter on diode regime and check source-to-drain - all power MOSFETs have a parasitic diode (and that could indeed be your problem) so that a MOSFET can be used as bilateral switch... Maybe the MOSFET is only partially fried...

[asbesto]

You should never do this again!

E 'GRAZI'ARCAZZO, saying in Roman Slang terms

It might be the TPC8109, if you're lucky, but chances are that you've fried something else. Look closely to the area beneath the touchpad - you should see the MAX1631 - controller chip for DC/DC converter on-board. This controller does the drop-out control, so your problem might have something to do with it.
South of MAX1631 there are 2 more MOSFET switches. You should check them as well.
Checking... Well, the best way is to pull them out with hot air, make a simple circuit and apply the voltage to the gate - see if the source (drain) current is rising as you raise the voltage from Gnd (NMOS), or lower it from Vdd (PMOS). The other, less informative way is to put a multimeter on diode regime and check source-to-drain - all power MOSFETs have a parasitic diode (and that could indeed be your problem) so that a MOSFET can be used as bilateral switch... Maybe the MOSFET is only partially fried...

many thx for this help, I will try those tests

[asbesto]

Well, I made some shoots and collected some data sheets of chips involved in this problem. Is all here:

http://spatof.org/asbesto/thinkpad

I'm going to make some measures soon...

[Kyocera]

In some cases it is OK to overamp when you are in the miliamp range, but underamping is usually when thing burn up.