Toshiba C660D no power

[rtstorm]

Hi, i got this toshiba C660D. When pluged in green led is on. When press power buton fan spin for 1sec and then stop. I check all fuse and they are ok. i see no physical damage on board.

PCB label is: LA-6843P des someone have schematic?? I use schematic for LA-6842P but it is not the same.

[rtstorm]

Re: Toshiba C660D no power

I check all fuse, and check caps with multimeter continuity test. i managed to find some shorted caps. I desolder them all but they are ok. I cannot find where is the short circuit. I found that reading on ISL6251 AHAZ a bit of strange.
Here are some pics.

I check coil without removing them and they all pass continuity test.

[whaldsz]

Re: Toshiba C660D no power

you can desolder the jumpers (example, PJ2 in image #2) so you can isolate which section is causing the shorts.

The short is not in the 19v rail right?

If no component is heating up, try to check the coil going to the GPU. If shorted, disconnect the coil and check which side is still shorted. If the load side (going to GPU) is shorted, then you need to replace this bga chip.

[rtstorm]

Re: Toshiba C660D no power

I try to do what you told me to do, and i find that when PJ7 is desoldered i can turn on the board, fan spins both led stay green. Ofc i don't have picture but it a start. Only component that is heating up is GPU. CPU is cold.

[whaldsz]

Re: Toshiba C660D no power

That means the short is in the pj7 rail.

[cyberhack]

Re: Toshiba C660D no power

Here you go

[rtstorm]

Re: Toshiba C660D no power

@cyberhack - thank you for diagram

I think i found where is the short cut. But i want your opinion. In picture attached i marked red rail where i get short cut, i think this should not have to be connected.
I found that Q13B - 2N7002DW-T/R7_SOT363-6 is N-channel FET, is it possible that that FET is bad? (page 31)

[rtstorm]

Re: Toshiba C660D no power

i desolder Q13B - 2N7002DW and it was ok, no shorts. i am confused

[khaahk]

Re: Toshiba C660D no power

Search for +NB_CORE in pdf. There is a possbility of northbridge short and there are some more caps (C180,C182...)also connected to the line.

[rtstorm]

Re: Toshiba C660D no power

i thik this is a northbridge short, i found on some other rails short. They all camo from NB.

I found shorted these on top of BGA.

[rievax_60]

Re: Toshiba C660D no power

What resistance are you calling a short? Some of those capacitors on the NB will measure about 20 ohms and some might even measure near 0 ohms. This is likely normal.

[rtstorm]

Re: Toshiba C660D no power

you are absolutely right! (rievax_60)

That made me think, and then I discovered that one MOSFET is shorted (in real therm SHORTED, GDS shorted) it was PQ41- MDU2653RH.

I connect PJ7 jumper back and it worked, i got the picture. I will order MDU2653RH although obviously laptop can work without it.

[rievax_60]

Re: Toshiba C660D no power

Well done.
Also that is why I sometimes say to not apply more than 1v test when finding a short. There might be a shorted High Side MOSFET sending the test voltage directly to CPU, NB or GPU.

[whaldsz]

Re: Toshiba C660D no power

nice work rtstorm!

[tomodachi]

Re: Toshiba C660D no power

well done ! Compal motherboards are can be easily repaired, and thanks for sharing.