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A laptop arrived at our service. complaint: no start onlaptop I connected the power supply. and there was a short circuitin the mains voltage. Because I noticed that the CPU gets hot when the mainvoltage comes on. i checked with my thermal camera yes cpu is getting hot. Istarted to examine over the sky. If the CPU is getting hot, it means one of itsmosfets is broken. I found a dual n channel mosfet with a short circuit
Dual n Channel MOSFET- was broken. and the upper mosfet init was short circuit. I also measured the mosfet outside. short circuit. Ireplaced the mosfet with a new one. and the short circuit problem is gone
So far, so good. I connected the motherboard to the powersupply. was in standby mode. I started and I'm happy. I said multiple endings.motherboard started. I immediately connected the ram and panel. I started. noimage  I thought it might be due to BIOS issue or RAM. I wrote theBIOS on the official site and tried other working RAM. unfortunately nothing iswrong. When I measured all the coils the voltages were all active. sequentiallywith the motherboard's signal timing, all required signals were active.
VCC_GT voltage seems strange to me. 0.6V. Because VCC_GTvoltage should rise momentarily and then become low after the motherboardstarts up. The operating system time needs to be increased. of course, avoltage that changes according to the image on the motherboard
then i connected post card
and error code 63. error codes were running normally when Ifirst started. and paused at last code 63. This code is actually an error coderelated to VCC_GT, that is, intel hd video card. It is more likely that the cpu is corrupt. because the CPUate 19V from the VCC_GT line
then the oscilloscope gives me a clue. I measured the SVIDDATA pin with an oscilloscope. Strangely enough (including CLK) I saw that thesignals were repeating one another. The same signals were sent over and over bythe CPU to the CPU VRM IC.
in this case the CPU VRM may be corrupted. Because if theupper mosfet is short-circuited, this 19V will go to both the CPU and the VRMIC.
Everything is clear in my head now. I need to change CPU.Customer accepted CPU replacement Yes, Intel's CPUs are very expensive.
For this reason, I found a cheap motherboard on ebay inworking condition. on Intel i5-7th gen. SoC CPU
and after that there was a difficult time for me. Iunplugged the CPU from the motherboard. I made a reball. and then soldered itto the other motherboard. everything went well. usually intel CPUs warp due toheat.
and happy ending 
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发表于 2023-5-5 04:46:01
会员1132538
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