Toshiba L855-10P Totally Dead

[grahamw01]

Re: Toshiba L855-10P Totally Dead

Vin goes through Q6010 first and all other pins but the voltage in are 0V, so isn't this a dead fet? I don't know how these work though, is it controlled and turned on through U6000? Ill check ACDET to GRND resistance now.

[laz]

Re: Toshiba L855-10P Totally Dead

Vin goes through Q6010 first and all other pins but the voltage in are 0V, so isn't this a dead fet? I don't know how these work though, is it controlled and turned on through U6000? Ill check ACDET to GRND resistance now.

graham, at Q6010 the pins 5-8 (Vin) are 19V.

[grahamw01]

Re: Toshiba L855-10P Totally Dead

Hi Laz, sorry for my lazy English, that's what I mean but pins 1-4 are 0V right? ACDET to GND is 3.3K (which s R6003) so even at 3.2K you should get roughly 2.5V

[laz]

Re: Toshiba L855-10P Totally Dead

i see, yes but i can't explain it. pins 1-3 are also input to pin3 U6000.

[khaahk]

Re: Toshiba L855-10P Totally Dead

The resistance from ACDET to GND might change after the U6000 receives its VIN and is powered on. Measuring resistance while powered on may not give correct answers though.
Q6010 will have the 19V at pins 1-4 after its gate (pin4) receives 25V from the U6000, which it will not give unless it gets ACOK 2.4-3.15V.

[grahamw01]

Re: Toshiba L855-10P Totally Dead

What is your resistance between pins 5-8 on Q6010 and pins 5-8 on Q6011? you should have 19V on all of these at all times, they are linked by R6015 and R6014 through D6002, what is D6002 pin 3-1 resistance?

[grahamw01]

Re: Toshiba L855-10P Totally Dead

On my board I am missing R6014, but R6015 is 4.68K (the resistor connected to pin 3 on D6002) you could check that

[laz]

Re: Toshiba L855-10P Totally Dead

What is your resistance between pins 5-8 on Q6010 and pins 5-8 on Q6011? you should have 19V on all of these at all times, they are linked by R6015 and R6014 through D6002, what is D6002 pin 3-1 resistance?

Hi graham, sorry last night my Internet connection had a very hard time.
R6014 is 4.6K, R6015 missing.
Resistance between pins5-8 Q6010 and pins5-8 Q6011 : 19,9K OR 17,3K (polarity dependent)
D6002 pins1-3 res.: 19,9K OR 16,6K (polarity dependent)

The resistance from ACDET to GND might change after the U6000 receives its VIN and is powered on. Measuring resistance while powered on may not give correct answers though.
Q6010 will have the 19V at pins 1-4 after its gate (pin4) receives 25V from the U6000, which it will not give unless it gets ACOK 2.4-3.15V.

khaahk, if U6000 is faulty, then the low voltage in ACDET would be explainable? Resistance ACDET to GND while connected to power is 87,3K. When not powered, 3,2K.

[laz]

Re: Toshiba L855-10P Totally Dead

It seems that others have similar issues with Toshiba's power circuits

https://www.badcaps.net/forum/showthread.php?t=21949

I believe that there is not much left to search for, except replacing the U6000...

[grahamw01]

Re: Toshiba L855-10P Totally Dead

Hi Laz, I think you are right, even just looking at ACDET there is nowhere else for that voltage to go. I will check the resistance from ACDET to GND powered on when I get home anyway and this should tell us. (about 5 hours)

[grahamw01]

Re: Toshiba L855-10P Totally Dead

Hi Laz, sorry for the late reply, there is no connection from ACDET to GND when AC is plugged in. I tried a bunch of times because I thought maybe I am not quite touching the pad, but I even had it so it would read 3.3k, then without moving plug in the AC and it instantly goes to no connection. I would say definitely a short in U6000!

[laz]

Re: Toshiba L855-10P Totally Dead

Hi Laz, sorry for the late reply, there is no connection from ACDET to GND when AC is plugged in. I tried a bunch of times because I thought maybe I am not quite touching the pad, but I even had it so it would read 3.3k, then without moving plug in the AC and it instantly goes to no connection. I would say definitely a short in U6000!

Hi graham, that explains a lot. Have you tried to measure with inverse polarity too?

[grahamw01]

Re: Toshiba L855-10P Totally Dead

Hi Laz, I just tried, (using + red lead on ground) it actually kills the laptop, LED power light goes off.. fortunately it came back on though!

[laz]

Re: Toshiba L855-10P Totally Dead

LOL, we don't want another dead Toshiba! Tomorrow i'll make an order and hopefully I'll post my results after a month. I am prepared for the worst though. Thank you for everything!!!

[grahamw01]

Re: Toshiba L855-10P Totally Dead

No problem, happy to (almost) help! I actually still have the one I bought in its original packet, never got round to fitting it as it wasn't required, you can have it for free if you just want to pay postage, I don't think a letter would cost much to send and might get to you quicker than from China

[laz]

Re: Toshiba L855-10P Totally Dead

I've already made the order. It's not expensive at all, but the delay from China is an issue. I'll wait, thanks a lot anyway!!

[grahamw01]

Re: Toshiba L855-10P Totally Dead

ah okay, well i hope it works for you!

[juliopolo18]

Re: Toshiba L855-10P Totally Dead

Laz Buen día , estuve leyendo el foro detenidamente y mi pregunta es lograste cambiar el IC U6000 . que tal quedo??
saludos

[kus234]

Re: Toshiba L855-10P Totally Dead

bios dump for this unit... any regards.. thanks

[Lex-]

Re: Toshiba L855-10P Totally Dead

I want to share the solution that worked for me...
Received a Toshiba Satellite L855, motherboard DK10F with same problem:

-> SYMPTOM <-
Totally dead

-> PROBLEM <-
Only 1.2V at ACDET (pin 6 of U6000 BQ24725) -> Normally near 2.7V

-> CAUSE <-
Voltage drop on ACDET caused by the PVBAT rail shorted to ground

-> SOLUTION <-
Using variable or lab power supply feed the PVBAT rail increasing the current or voltage (do not exceed 19V), until the component causing the short becomes hot, in my case the failed component was the ceramic capacitor C6110 (or C6111), near Q6100, rated at 4.7uF 25V

-> NOTE <-
Also discovered FUSE6050 15A open, replaced it too