PPVRTC_G3H short to ground (Visual inspection for corrosion)Įxample: (65mA on charger, "Few KiloOhms" short to ground on PPVRTC_G3H caused by corroded capacitors).Keyboard bad, shorting PP3V42_G3H to ground or power button stuck on.SMC not working(if SMC is off, you will have 12.23v on PPBUS_G3H instead of 12.56v) because it is dead, not turning on(SMC_RESET_L low).16-20v on ADAPTER_SENSE means charger voltage is leaking into ADAPTER_SENSE, below 2v means it is missing usually due to a bad DC in board. ADAPTER_SENSE not 3v due to bad DC in board.Remove the switch, verify that the laptop now turns on. USB port power switch chip is blown, badly soldered.PM_SLP_S4_L and PP5V_S3 are missing, i.e.Unplug it, see if it works(short on 3.3v or 5v rail on the I/O board can cause this problem). Sometimes shotgun replacement of the chip is a clean solution. PM_SLP_S4_L missing for random reason, thoroughly inspect clock chip, tiny specks of corrosion next to it can kill it.U7100 ISL6259 bad, shorted current sense resistors R7121 & R7122 to ground through the U7100.Įxample on 820-00426: Resistors were bad and the ISL6259 was bad too. Replacing the bad capacitor fixed the problem. Ethanol used instead of thermal cam with 0.7V on PPBUS_G3H, resistance between PPBUS_G3H and CPU coil is 22Ohm)Ģ68mA current draw, visual inspection reveals cracked tantalum capacitor was causing the short. If PPBUS_G3H to CPU/GPU vcore coils is not under 1 ohm, the short is elsewhere, inject 1v and use thermal camera to help you find the short.Įxample of bad capacitor: (Taking 0.2A. On this board this situation is always a no fix, since 12v fried the CPU. Measure PPBUS_G3H to vCORE coils (coils around CPU/GPU) IF those measure UNDER 1Ohm (0.3-0.8) then you most likely have a direct 12V short to CPU/GPU. Best to repair the corroded area(s) before connecting the machine to a power source. If there is corrosion in the U7200 area it is not a good idea to connect the charger because there is a chance that it will send 12V to the CPU and kill it (or the CPU is dead already). DO NOT use FDMF 6808 chips from a donor board. The failing CPU MOSFETs can be replaced with FDMF 6708 or FDMF 3030 chips. Kernel panics with failing CPU MOSFETs are very uncommon, and suggestive of another problem. With failing CPU MOSFETs, people will report a black screen followed by a restart or shutdown. This has been confirmed with x-ray inspection. On late 2013 through 2015 devices, the issue is likely failing CPU MOSFETs.
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