Hi there, I am working on the Toshiba C55 laptop listed in the title and I am kind of stuck. I am very familiar with electronics but I have never tried to fix a laptop at the component level before and I am flying blind without any sort of schematic. I will attach some pictures to the bottom but I will go over what has happened to the machine, what I have done and where I am now.
I got the laptop for free from a friend cause it was broken, power led blinks continuously when you try to turn it on, AC or battery. I took it apart and what I found was that the laptop was dropped with a wireless mouse dongle in the usb 3.0 port. The port sheared from its solder point and removed the chokes on the data lines, I found the windings through out the laptop. I initially thought they shorted something, its still possible but inductor windings are coated so I'm not so sure now. I also checked to make sure that there were no shorts across any of the usb power/data pins. When the memory is removed the system stays powered up allowing me to check the voltages present on the board. If I reinsert the ram the system goes back not booting with the power led blinking, if you leave it on long enough the fan stars.
From there I measured all the fuses I could fine, checked the voltage on the bios chip and scoped its output, seems fine but ultimately there is no way for me to know if the data is good. Next I checked the voltages on all the big caps near the voltage regulators and thats where I found a symptom.
The circled cap in one of the pictures below, which is near the cpu has no voltage across it at all. From poking around it appears that it is the power supply for the RAM, I just did a simple continuity test and assumed that the cpu and other major components had their own dedicated supply. I checked Q6710 and there is voltage across the source and drain so voltage is available but the mosfet is not switching. Next I scoped the gate pin of the mosfet and there is no signal to it, I also scoped a different mosfet where there is voltage across its cap and you can see the switching signal. I checked the mosfet and I do believe that it is fine. I couldn't however find what controls that mosfet, its damn near impossible to trace things on these multi layer boards, unless I start dragging my probes across everything and that could damage the mosfet.
From here I am not sure where to go, I don't have a schematic (board is db10f-6050a2566201-mb-a02) and I really don't know if whatever is supposed to switch that mosfet is working or not or if some command in the bios is corrupted and not turning it on. I would defiantly appreciate any advice from anyone who has some to give.
Thanks in advance.
I got the laptop for free from a friend cause it was broken, power led blinks continuously when you try to turn it on, AC or battery. I took it apart and what I found was that the laptop was dropped with a wireless mouse dongle in the usb 3.0 port. The port sheared from its solder point and removed the chokes on the data lines, I found the windings through out the laptop. I initially thought they shorted something, its still possible but inductor windings are coated so I'm not so sure now. I also checked to make sure that there were no shorts across any of the usb power/data pins. When the memory is removed the system stays powered up allowing me to check the voltages present on the board. If I reinsert the ram the system goes back not booting with the power led blinking, if you leave it on long enough the fan stars.
From there I measured all the fuses I could fine, checked the voltage on the bios chip and scoped its output, seems fine but ultimately there is no way for me to know if the data is good. Next I checked the voltages on all the big caps near the voltage regulators and thats where I found a symptom.
The circled cap in one of the pictures below, which is near the cpu has no voltage across it at all. From poking around it appears that it is the power supply for the RAM, I just did a simple continuity test and assumed that the cpu and other major components had their own dedicated supply. I checked Q6710 and there is voltage across the source and drain so voltage is available but the mosfet is not switching. Next I scoped the gate pin of the mosfet and there is no signal to it, I also scoped a different mosfet where there is voltage across its cap and you can see the switching signal. I checked the mosfet and I do believe that it is fine. I couldn't however find what controls that mosfet, its damn near impossible to trace things on these multi layer boards, unless I start dragging my probes across everything and that could damage the mosfet.
From here I am not sure where to go, I don't have a schematic (board is db10f-6050a2566201-mb-a02) and I really don't know if whatever is supposed to switch that mosfet is working or not or if some command in the bios is corrupted and not turning it on. I would defiantly appreciate any advice from anyone who has some to give.
Thanks in advance.
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