Hi, i'm trying to fix this notebook with the 19v missing on the main power rail.
It's an old Toshiba Satellite L750D.
The CPU (an AMD Phenom II) can be removed but the GPU is soldered.
Mainboard model: DABLCDMB8E0 REV E.
The notebook isn't mine, and it was in pretty bad condition.
Other than be full of dust and with broken parts, i also found this problems:
1) the DDR3 ram was half-disconnected, and 1 smd capacitor near the memory chips seems burned (photo n1);
2) in the mainboard another one smd capacitor was not soldered, but near the original position (n2).
I cleaned all with IPA, soldered again the disconnected capacitor, removed the burned ram, the CPU (i don't know if still good or not) and all the other things.
The power supply it's fine (19v when is not connected to the mainboard).
Connected to the mainboard, i can hear the power supply "clicking", and the voltage drop at 2-2.5v (unstable).
After many minutes, only the up-left part of the board become a bit hot (both sides A-B), and seems that is one of the big mosfet that heat the pcb.
But still, nothing that is "burning hot".... ( photo n3 "mainboard zoom SIDE A").
In that mosfet, the voltage is 2-2.5v in input (right), and 1-1.2v in the output (left).
Around the board, stuffs near the cpu socket, gpu etc are cold, with 0v or 0.100-0.300v.
In the photo n4 "plus signal SIDE B" (taked after i dismantled the notebook) i "painted" where the plus DC signal start in one side of the board (the PC24 capacitor was the one disconnected that i soldered again).
So + +, PF2 fuse, then PL1/PL2, PD4, PC39, PD3, PD5, PR38, PQ2, and then other things until the ISL88731C battery chip.
Other than the fuse that is good, i can't be sure about all the other parts.
Starting from the right side of PD3, there is a resistance of about 200 ohms from the left side (and the plus start). Maybe is ok but again i'm not sure about it.
I did a sort of "schematic" for both sides (n3 - n4), and also tested some capacitors with the ohms values to ground.
Say me if more details is needed, or what tests i have to do.
I'm new in the "component level repair" world, just watched some videos on yt, read of similar problems in the internet and also the beginner's guides here.
Honestly, i learned few stuffs starting from 0, but still can't find the problem or how to test the main power rail correctly in this mainboard.
I disconnected some capacitors near that battery chip and the two big mosfets in the other side of the board.
The capacitors that i tested are all fine but i'm not sure about how to test the 2 big mosfet.
The notebook is old and not important, but i really want try to fix it, like a personal challenge!
Thanks for the help and sorry if i did any errors! ^^"
It's an old Toshiba Satellite L750D.
The CPU (an AMD Phenom II) can be removed but the GPU is soldered.
Mainboard model: DABLCDMB8E0 REV E.
The notebook isn't mine, and it was in pretty bad condition.
Other than be full of dust and with broken parts, i also found this problems:
1) the DDR3 ram was half-disconnected, and 1 smd capacitor near the memory chips seems burned (photo n1);
2) in the mainboard another one smd capacitor was not soldered, but near the original position (n2).
I cleaned all with IPA, soldered again the disconnected capacitor, removed the burned ram, the CPU (i don't know if still good or not) and all the other things.
The power supply it's fine (19v when is not connected to the mainboard).
Connected to the mainboard, i can hear the power supply "clicking", and the voltage drop at 2-2.5v (unstable).
After many minutes, only the up-left part of the board become a bit hot (both sides A-B), and seems that is one of the big mosfet that heat the pcb.
But still, nothing that is "burning hot".... ( photo n3 "mainboard zoom SIDE A").
In that mosfet, the voltage is 2-2.5v in input (right), and 1-1.2v in the output (left).
Around the board, stuffs near the cpu socket, gpu etc are cold, with 0v or 0.100-0.300v.
In the photo n4 "plus signal SIDE B" (taked after i dismantled the notebook) i "painted" where the plus DC signal start in one side of the board (the PC24 capacitor was the one disconnected that i soldered again).
So + +, PF2 fuse, then PL1/PL2, PD4, PC39, PD3, PD5, PR38, PQ2, and then other things until the ISL88731C battery chip.
Other than the fuse that is good, i can't be sure about all the other parts.
Starting from the right side of PD3, there is a resistance of about 200 ohms from the left side (and the plus start). Maybe is ok but again i'm not sure about it.
I did a sort of "schematic" for both sides (n3 - n4), and also tested some capacitors with the ohms values to ground.
Say me if more details is needed, or what tests i have to do.
I'm new in the "component level repair" world, just watched some videos on yt, read of similar problems in the internet and also the beginner's guides here.
Honestly, i learned few stuffs starting from 0, but still can't find the problem or how to test the main power rail correctly in this mainboard.
I disconnected some capacitors near that battery chip and the two big mosfets in the other side of the board.
The capacitors that i tested are all fine but i'm not sure about how to test the 2 big mosfet.
The notebook is old and not important, but i really want try to fix it, like a personal challenge!
Thanks for the help and sorry if i did any errors! ^^"
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