Dead Sony VAIO Duo 13 (MBX-281)

[damatg]

Hi everyone,
I just bought a dead Sony VAIO Duo 13 ... and I'm willing to restore it to its past glory!

The device has been already opened, and a clear sign of this is a broken flat cable that connects the power switch and the charge led to the motherboard.

Unfortunately this seems to be just one of the laptop's problems, here's my troubleshooting.

I disconnected everything from the motherboard (even the main battery), except the fan.

Charger's output is 10.5v. This voltage is present at the motherboard, and passes the first fuse.

Voltage at the power button pin is 3.3v as soon as i attach the power supply.

I checked the voltage at the various power inductors. It is 0v, but if I pull down to ground for some seconds the power button pin, I get 5.1v and 3.3v at two of the coils (tomorrow I'll try to contextualize with some pics).

All other power inductors remain at 0v even after simulating the power button pressure. Nothing seems to get particularly hot in this case.

If the main battery is connected to the motherboard, something interesting happens. One third power inductor goes to 8.5v. However, after simulating the power button pressure it becomes hot (battery pack rating is 7.5v), along with an adjacent mosfet and a couple of passive components (and battery charger IC, BQ-24735) on the other side of the board (tomorrow I'll try to contextualize with some pics).

No power at the Winbond flash, no power at USB ports.

Some questions for you people:
1. Is it possible that this laptop can't be powered on without battery? Why the "getting hot" fault is showing only in this occasion?
2. It seems a possible case of a shorted cap ... but why does it show up only if the battery is connected?
3. Why 5.1v and 3.3v show up only after power switch is pressed? Even though somehow a low power 3.3v rail is always there, since it's always present at the power switch (is this a sign that the Super I/O chip is good?).
4. Someone has a board diagram for this board?
5. I checked some enable signals (I'll repeat the test tomorrow though) at voltage regulator TPS-51367 and it seems 0v ...

I'll dedicate some more time to study it asap, please follow this thread and give me suggestions!

[Techtiger]

Re: Dead Sony VAIO Duo 13 (MBX-281)

what are the voltage's with battery & with out battery all pins of TPS-51367 BQ-24735
for some plate forms you cant power the board with out battery ? Sony have a different Architecture the ALW come after PWRBTW LDO 3/5V must come 1st uplode a PIC of the olny the MB both side

[damatg]

Re: Dead Sony VAIO Duo 13 (MBX-281)

Hi, thank you for your reply!
I further analyzed the situation.

Today, with battery attached, the behavior of the motherboard was (somehow) a bit different.

Infact, the "hot" components never become hot, and sometimes it was not necessary to simulate the power button to make 5V and 3.3V show up. When this was not the case, 5V and 3.3V were present right after the power cord was connected, and then went to 0V in some seconds.

I checked the voltages at the two ICs (image attached).
Basically TPS51367 is not powering on ... EN is 0V and VREF is 0V (well, this is actually not really exciting ...).

BQ24735 seems fine, i think that ACOK is 0V just because it seems there's no pull up resistor.