Hi,
I have a nonworking laptop Toshiba L50-B-245 with motherboard DABLIDMB8E0 REV E. When I plug in a charger, I get a charging light. When I press the power button, the power light blinks once and I also get a short fan spin. Sometimes both lights blink. I tried to search for short on the board, but I couldn't find any.
After many tries I managed to turn the laptop on, but I didn't get anything on screen. So I did some measurements and I found out that the GPU has no voltage. The GPU VRM is controlled by ISL62771 chip. This chip has an enable pin, which should be high to start the VRM. But there was 0V on that pin. So I turned the laptop off and it didn't want to start again.
When I press the power button I see on my multimeter that the voltage on the enable pin goes to 0.5V and then back to zero. So I guess that the chip gets 5V for a very short moment, but my multimeter isn't quick enough to sense that. I tried to supply 5V on that pin and I got 0.8V on the GPU. So I guess that the GPU VRM is OK, it just doesn't get enabled.
So now I'm stuck and I don't know how to continue the troubleshooting. My guess is that the chip generating this enable signal is faulty, but I don't know which chip it is. I tried to search for schematics but I couldn't find it. Does this signal come from the startup chip (or whatever it's called, on this board it's Nuvoton NPCE985LA0DX)? I tried measuring, but I couldn't find any pin on the startup chip directly wired to the enable pin.
I'm just a beginner, so I might be missing something obvious. But I'd like to learn. I tried to search this forum and other sites for similar issues, but I couldn't find any. Could someone please help me or just point me to a right direction? If you need more information, just ask and I will gladly provide it
I have a nonworking laptop Toshiba L50-B-245 with motherboard DABLIDMB8E0 REV E. When I plug in a charger, I get a charging light. When I press the power button, the power light blinks once and I also get a short fan spin. Sometimes both lights blink. I tried to search for short on the board, but I couldn't find any.
After many tries I managed to turn the laptop on, but I didn't get anything on screen. So I did some measurements and I found out that the GPU has no voltage. The GPU VRM is controlled by ISL62771 chip. This chip has an enable pin, which should be high to start the VRM. But there was 0V on that pin. So I turned the laptop off and it didn't want to start again.
When I press the power button I see on my multimeter that the voltage on the enable pin goes to 0.5V and then back to zero. So I guess that the chip gets 5V for a very short moment, but my multimeter isn't quick enough to sense that. I tried to supply 5V on that pin and I got 0.8V on the GPU. So I guess that the GPU VRM is OK, it just doesn't get enabled.
So now I'm stuck and I don't know how to continue the troubleshooting. My guess is that the chip generating this enable signal is faulty, but I don't know which chip it is. I tried to search for schematics but I couldn't find it. Does this signal come from the startup chip (or whatever it's called, on this board it's Nuvoton NPCE985LA0DX)? I tried measuring, but I couldn't find any pin on the startup chip directly wired to the enable pin.
I'm just a beginner, so I might be missing something obvious. But I'd like to learn. I tried to search this forum and other sites for similar issues, but I couldn't find any. Could someone please help me or just point me to a right direction? If you need more information, just ask and I will gladly provide it
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