Toshiba C50D-A133 - one problem after another

[paulo66]

PT10AN DSC MB REV 2.1
AMD E1, no discrete GPU. 4Gb RAM.

A colleague at work knowing I'm an electronics hobbyist brought this dead laptop to see if I could fix it. It has never been serviced.

Tons of dust cleaned. There was no 19V. There were two ceramic caps near the fan and one of them was shorting the B+ to ground.

Cap removed, the unit turned on and battery was charging. Fan not spinning. No image. 3,3 and 5V present. No shorts across the coils.

Reflashed the BIOS with some .bin file found here. Now everything was working, except the fan. Upon power on the fan would spin for a quarter of a turn and stay still. I swear I saw it spinning at one time, while Windows was booting. But that was the only occasion. The OS was password protected and since then I tried boot using a few other HDs without success. It would only accept the "original" HD.

Since the ceramic caps in tandem were near the fan, I finally added a good capacitor in place of the shorted one. No luck, just a quarter of a turn and that was it.

As I was visually inspecting the board, then suddenly the white LED turned off. Removed the new cap, and the unit doesn't power on anymore!

A QFN20 sitting next to the +3.3V and the +5V coils is burning hot. By God, is this another !"#$%& EC dead issue? The caps around the IT8528E appear shorted to ground...

[paulo66]

Re: Toshiba C50D-A133 - one problem after another

Something unexpected:

Removed the EC because there is what looks like a scratch but could be a burn mark. But the short was still there.

Pin 8 of the BIOS chip was also shorted. Removed chip. Short on the MB was still present, but BIOS chip measured fine.

Put BIOS back in place. Short is totally gone. Whatever...

CAN I TURN THE MB ON WITHOUT THE EC? Just to check if the regulator is OK...

[Techtiger]

Re: Toshiba C50D-A133 - one problem after another

No Don’t do it depends on the platform some of the regulates need EC feed back

[paulo66]

Re: Toshiba C50D-A133 - one problem after another

Makes sense. Thanks.

I'll order new chips.

[paulo66]

Re: Toshiba C50D-A133 - one problem after another

I soldered the EC back into place hoping it had been nothing but a glitch. Three legs at a corner got bent and I lifted a pad while trying to straighten then. I can repair it, no problem. Worst thing is the reg still gets hot.

Think I'd better quit this hobby. It's quite interesting, but my success rate is too low and it can be frustrating and time-consuming. People like Sorin, Jessa and John Gammel make it appear too easy.

[paulo66]

Re: Toshiba C50D-A133 - one problem after another

The 1225C reg was near impossible to desolder. Like it had fused itself with the motherboard. Three pads missing. It´s finished.

[Smoxx]

Re: Toshiba C50D-A133 - one problem after another

It's possible to recover those pads or jump the IC with some patience and skills (and a microscope, OFC)

What temperature do you use on the rework station? Are you using good flux? Some PCB may require lower temperatures and using good flux is mandatory to avoid such "accidents".

[paulo66]

Re: Toshiba C50D-A133 - one problem after another

I got two microscopes, one "Andonstar" type with built-in display and a "dental" stereoscope. Cheap, but they get the job done.

In addition to the missing pads the vias to ground look busted.

Soldering stations are new to me. I have trouble choosing the right temperature. I still think in terms of Watts. I used a Hakko Presto soldering iron for more than a decade. It can go from 20W to 100 by pressing a button. It´s great for through-hole.

For SMD I´ve been using a genuine FX-888D because there are plenty of tips to choose. Problem is it uses the T18 while most available are 900M so I have to either choose a higher temp setting or wrap the heat element with copper foil for better thermal coupling.

I usually choose 270ºC and 320ºC for the iron. And for the hot air Sorin says to use the highest temperature and full air speed. So I go 500ºC. 400ºC when it gets painful to hold the tweezers.

IDK lower temperature and slower air does make more sense. Higher temp and velocity may lead to thermal shock.

Flux is usually no clean liquid by Thermopasty, flux paste by Nevex. Sometimes just colofonia and IPA. ChipQuik flux doesn´t seem to work, Amtech is expensive and the chinese RMA223 is crap.

[paulo66]

Re: Toshiba C50D-A133 - one problem after another

Do you have any idea on what could have caused the fan issue?

[Sametbey]

Re: Toshiba C50D-A133 - one problem after another

2-pin rev counter of j5001 fan socket. ITE this will be a check-up. U5002 chip fan control. Pin 4 is the control PIN.

[paulo66]

Re: Toshiba C50D-A133 - one problem after another

Thank you.

The Vin was there. The fan would spin a quarter turn and stop. Maybe the EC was sending an "are you there" signal and wasn't getting feedback from the Voltage return pin 3.

[paulo66]

Re: Toshiba C50D-A133 - one problem after another

Just git hold of a second motherboard. This one is dead but so was the other. This one has descrete gpu unlike the other. If I bring it to life I'll have to either remove it or find a suitable cooler.

[paulo66]

Re: Toshiba C50D-A133 - one problem after another

No +3.3VAO and no +5VAO, but there is +3.3V at the power switch and at pin 8 of the BIOS. Nothing on pin 1. EC doesn´t seem dead and there are +5V present on some pins of the 1225C. The LDO probably, although no +3.3V.
Already tried a reflash, gonna try another.

Does anyone have a better idea? Please share. Thank you.

[Techtiger]

Re: Toshiba C50D-A133 - one problem after another

No +3.3VAO and no +5VAO, but there is +3.3V at the power switch and at pin 8 of the BIOS. Nothing on pin 1. EC doesn´t seem dead and there are +5V present on some pins of the 1225C. The LDO probably, although no +3.3V.
Already tried a reflash, gonna try another.

Does anyone have a better idea? Please share. Thank you.

Upload the Schematic

[paulo66]

Re: Toshiba C50D-A133 - one problem after another

Good advice often given here, to always make a backup of the firmware. It may be needed later.

The post above may sound confusing and even wrong.
No schematic, no boardview. Trying to layout my thoughts and be least intrusive.

- There is +19v all over the board. It's powering the linear and switching functions of the 1225c regulator.

- The linear +5v is present at some test point close to the regulator.

- The linear +3.3v is present, feeding the bios and ec chips.

- The pwm generators seem to be waiting for a powergood line from the ec. To be verified.

- The non-programmable ec is alive. It's sending out the +3.3v powerbutton line. Hope it's by default.

- The bios is alive. Pin 1 is not active. Hope it's data output pin. Easier to replace a faulty eeprom than a nonresponding ec.

-

[paulo66]

Re: Toshiba C50D-A133 - one problem after another

Ah pin 1 chip select, active low, so it's working. That's a relief.

[paulo66]

Re: Toshiba C50D-A133 - one problem after another

I can´t believe this s**t happened again.

Just got another non-working motherboard, this time identical to the first. Charge port ferrite inductor was open, shunted it with a wire. A decoupling capacitor from the B+ to the CPU was shorted, removed it. Second MOSFET was open, shunted with a wire. Managed to power the unit up, with power LED on, fan spinning, all voltages present. Powered it down, plugged the display, no image. No LED either. Buck converter burned my fingers