Hi,
Recently I received a NM-B891 board from a ThinkPad T490s with signs a abuse: around the TBT and BIOS chip many components were missing (probably from too much hot air) and the board was flooded with flux in many places. I replaced all missing parts according to the schematic and boardview, I replaced the TBT and the BIOS chip with new and flashed chips and I replaced a blown fuse of the power LED. Now the situation is as follows: when plugging in the charger the charge LED lights up and the power LED blinks 3 times. When I press the power button the power LED lights up, the fan starts spinning for a few seconds, the current briefly jumps to 600 mA, then drops to 500 mA and stays there, but there is no picture. All rails are ok, the CPU gets warm. A thermocam doesn't show any hotspots. The CLK port of the BIOS chip shows activity on an osci for about 1 second, but no more. All 3 crystals have a clear, undistorted signal. I measured the following signals:
CPU_PWRGD 1,0 V on TP1301
VCCST_PWRGD 1,0 V on R1322
CPUCORE_PWRGD 3,3 V on PR0807
DRAMRST 1,2 V on R0504
RSMRST 3,3 V on ThinkEngine
RTCRST 3 V on J1701
PLTRST# 3,3 V on U1301 Pin 4
What else can I do?
schematics and boardview can be found here: https://www.badcaps.net/forum/showthread.php?p=1152211
Recently I received a NM-B891 board from a ThinkPad T490s with signs a abuse: around the TBT and BIOS chip many components were missing (probably from too much hot air) and the board was flooded with flux in many places. I replaced all missing parts according to the schematic and boardview, I replaced the TBT and the BIOS chip with new and flashed chips and I replaced a blown fuse of the power LED. Now the situation is as follows: when plugging in the charger the charge LED lights up and the power LED blinks 3 times. When I press the power button the power LED lights up, the fan starts spinning for a few seconds, the current briefly jumps to 600 mA, then drops to 500 mA and stays there, but there is no picture. All rails are ok, the CPU gets warm. A thermocam doesn't show any hotspots. The CLK port of the BIOS chip shows activity on an osci for about 1 second, but no more. All 3 crystals have a clear, undistorted signal. I measured the following signals:
CPU_PWRGD 1,0 V on TP1301
VCCST_PWRGD 1,0 V on R1322
CPUCORE_PWRGD 3,3 V on PR0807
DRAMRST 1,2 V on R0504
RSMRST 3,3 V on ThinkEngine
RTCRST 3 V on J1701
PLTRST# 3,3 V on U1301 Pin 4
What else can I do?
schematics and boardview can be found here: https://www.badcaps.net/forum/showthread.php?p=1152211
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