Toshiba L50-B dead MBO

[Gavran]

Laptop: Toshiba L50-B-1R1, MBO DA0BLIMB6F0 REV:F

Problem: If I plug in AC and/or battery laptops starts by itself, fan starts spinning for about 5 seconds than stops, Num, Caps, Pwr and wifi leds are illuminated. CPU is overheating by just sitting there. Screen is blank and no backlight, no beeps, laptop can't be turned off. Wifi led can be turned off by Fn+F12 but Caps and Num can't. Problem appeared "by itself", one day it was working, next morning this.

Diagnosis: Tried normal procedures (draining residual power, resetting by G2 jumper, BIOS reflash via external programmer) but non helped.

Voltages before PWR button press:
RT6575A : All 4 rails give power, 3v3 LDO, 3v3 SW, 5v LDO, 5v SW
BIOS ROM : 0.7V
NPCE985LA0DX : AVCC(102)=3.3v, VCC(115)=3.3v, NBSWON#(95)=reacts to button press, DNBSWON#(91)=0v, RSMRST#(75)=0v, SUSC#(73)=3v, SUSB#(94)=0v, SUSON#(22)=3v

Voltages after PWR button press:
RT6575A : All 4 rails give power, 3v3 LDO, 3v3 SW, 5v LDO, 5v SW
BIOS ROM : 0.7V
NPCE985LA0DX : AVCC(102)=3.3v, VCC(115)=3.3v, NBSWON#(95)=reacts to button press, DNBSWON#(91)=2.6v, RSMRST#(75)=0v, SUSC#(73)=3v, SUSB#(94)=0v, SUSON#(22)=3v

Any tips what might help?

[Techtiger]

Re: Toshiba L50-B dead MBO

Your Bios isn’t' getting 3.3V pin 8 form 3v3 LDO upload the schematic & for the Bios you have to flash it from bios programmer tool you can buy it from Ebay low cost
RSMRST#(75)=0v it should be 3.3V Most probably 3V &5V regulator or test the power rail Bios pin 8 connected SMD components suspected

[Gavran]

Re: Toshiba L50-B dead MBO

I don't have a schematic. I traced transistor that turns on 3v3 for BIOS, but it has same 0.7v on drain, and 1.2v on gate. I wasn't able to trace where that 0.7v comes from cause it is lost on some mid layers.
Do you know where is BIOS pwr generated on this MBO?

I flashed BIOS ROM with Raspberry PI and flashrom tool. ROM was extracted from .fd file downloaded from toshiba site. I just truncated headers in .fd file to get 8MB .bin file. Don't know if it is a valid way of doing, or i should prepare the dump before flashing.

[Techtiger]

Re: Toshiba L50-B dead MBO

I don't have a schematic. I traced transistor that turns on 3v3 for BIOS, but it has same 0.7v on drain, and 1.2v on gate. I wasn't able to trace where that 0.7v comes from cause it is lost on some mid layers.
Do you know where is BIOS pwr generated on this MBO?

I flashed BIOS ROM with Raspberry PI and flashrom tool. ROM was extracted from .fd file downloaded from toshiba site. I just truncated headers in .fd file to get 8MB .bin file. Don't know if it is a valid way of doing, or i should prepare the dump before flashing.

for the Bios power is generated from the RT6575A pin 3 (3.3V LDO) make a request on the Schematic section for the your Schematic as for Raspberry PI and flash rom tool I haven't done it so no idea , send a close up PIC of near BIOS Chip the components near we will try to trace it

[on/off]

Re: Toshiba L50-B dead MBO

Determine it does bios 3V or 1.8V with see marking code on top IC.

Also CPU heating only when plug in, seem not good on circuit or cpu has fallen.
Quanta for toshiba BLID, BLIM schematic unavailable right now (very weird, other brands present)

[Gavran]

Re: Toshiba L50-B dead MBO

BIOS chip is GD25Q64B, it is 3v3.
Are you sure it is powered via RT6575A 3v3 LDO? Cause it has no continuity from mosfet to RT6575A. I will post some photos soon.

[Techtiger]

Re: Toshiba L50-B dead MBO

BIOS chip is GD25Q64B, it is 3v3.
Are you sure it is powered via RT6575A 3v3 LDO? Cause it has no continuity from mosfet to RT6575A. I will post some photos soon.

Yep GD25Q64B is the Bios IC it's not a Mosfet diffrent function,powered via RT6575A 3v3 low dropout

[Gavran]

Re: Toshiba L50-B dead MBO



Higher res:
https://ibb.co/PcRz05Z
https://ibb.co/WHQvTdY
https://ibb.co/k8PfnCy
https://ibb.co/Hd9sMGn
https://ibb.co/x5kKg4D

[Gavran]

Re: Toshiba L50-B dead MBO

Mosfet is controlling power to BIOS, but that power rail isn't connected to RT6575A 3v3 LDO rail, no continuity to it.

[piernov]

Re: Toshiba L50-B dead MBO

Take off the heatsink and check which part of the CPU package is heating up. (smaller die is PCH, larger die is the actual CPU)

Which coils have power and which don't?

[on/off]

Re: Toshiba L50-B dead MBO

Does Mosfet Q11 is AO3404?

[SMDFlea]

Re: Toshiba L50-B dead MBO

Does the main battery power RTC on this board ? .

[Gavran]

Re: Toshiba L50-B dead MBO

Taken off the heatsink, smaller die is heating up, larger die is cold.

Voltages on switcher ouputs (before pwr button press) are :


Higher res : https://ibb.co/QrDGvD5

After pwr button press, coil near the fan outputs 1.7v, others stay the same.

Q11 is marked with ADLV 14, don't know if its AO3404.

Board has no onboard battery for RTC, so it might be powered via main battery.

[Gavran]

Re: Toshiba L50-B dead MBO

I probed whole board for BIOS pwr rail, and I end up on single capacitor under the CPU.
Other components connected to it are some pullups and both gates on one 2N7002KDW-GP. 2N7002KDW-GP has 3v3 on both drains, and they are connected to KBC(67) and KBC(68).
Could it be that PCH is powering BIOS? Or this PCH only has pwr inputs? CPU is i7-4510U.

[Techtiger]

Re: Toshiba L50-B dead MBO

since RT6575A is output 3.3V LDO your BIOS is power by LDO not the PCH with out the exact or similar Schematic it is difficult to trace

[Gavran]

Re: Toshiba L50-B dead MBO

Bios pwr? isn't BIOS pwr rail, i got that wrong.
BIOS pwr rail comes from another mosfet and 3v3 SW rail (not LDO). Mosfet is OK, but no signal on gate. That signal should come from PCH_PWR_EN# according to some other schematics. I tried bridging the mosfet to get 3v3 on BIOS, now PCH heats less, but nothing else changed.
What are the odds that PCH or KBC failed?

[Techtiger]

Re: Toshiba L50-B dead MBO

Bios pwr? isn't BIOS pwr rail, i got that wrong.
BIOS pwr rail comes from another mosfet and 3v3 SW rail (not LDO). Mosfet is OK, but no signal on gate. That signal should come from PCH_PWR_EN# according to some other schematics. I tried bridging the mosfet to get 3v3 on BIOS, now PCH heats less, but nothing else changed.
What are the odds that PCH or KBC failed?

uplode the schematics that you have, SOC Mob PCH integrated ?, do you have RSMRST# ?

[Gavran]

Re: Toshiba L50-B dead MBO

I used this schematic for reference only : https://www.badcaps.net/forum/showpo...71&postcount=2

PCH is integrated on SoC.
RSMRST# is still 0V, after I bridged 3v3 to BIOS pin8.

[Gavran]

Re: Toshiba L50-B dead MBO

On this MBO i have one more ROM (U17) marked with 4G08 41223. It could be ST24C08, it's pins 5 and 6 are connected to KBC 67 68.
Is it the EC ROM? Anyone have dump for it?

[piernov]

Re: Toshiba L50-B dead MBO

RSMRST# pin on the EC can be different from board to board as it's a simple GPIO driven in software by the EC firmware. If you get CPU VCore and RAM voltage you're in a S0 state, well beyond RSMRST# (which would prevent entering an S4 state).
Hard to know what could be wrong, but as a random suggestion I'd try to flash the BIOS with a known working dump.
Could be bad EC, could be random stuff on the board, but this is confusing as you have all rails for S0 state but the BIOS doesn't have 3.3V

I don't think the other ROM U17 is the EC firmware, EC firmware is most likely integrated into the BIOS.

I'd recommend taking a look at Quanta BDBD schematics which should have much more similarity than Compal LA-B301P