EMB-6011 motherboard does not show maintenance when it is turned on

EMB-6011 motherboard does not show maintenance when it is turned on.

Main board version number: EMB-6011(H81 chipset)

Fault phenomenon: the boot does not display.

Maintenance process:

This is a motherboard of Previously repaired, and PCH has been repaired.

EMB-6011 motherboard does not show maintenance when it is turned on Figure 1.

EMB-6011 mainboard does not show maintenance figure 1 when it is turned on.

EMB-6011 motherboard does not show maintenance when it is turned on Figure 2.

Measure the ground value of each VCC, which is normal. Install CPU and memory, and there is no display when powered on. Measuring memory VCC 1.33V

EMB-6011 motherboard does not show maintenance when it is turned on Figure 3.

VCC 1.05V bridge.

EMB-6011 motherboard does not show maintenance when it is turned on Figure 4.

According to the drawing, buses VCC and IO VCC are all converted from bridge VCC through resistance, and the actual measurement is normal.

EMB-6011 motherboard does not show maintenance when it is turned on Figure 5.

When CPU VCC is measured, it is found that there is no CPU VCC, which is H81 motherboard, according to the timing of 8 series.

EMB-6011 motherboard does not show maintenance when it is turned on Figure 6.

When all VCC are normal, CPU VCC will be generated, and when it is normal, SYS_PWROK will be generated. SYS _ PWROK in VCC comes from the PG phase of SLP_S3# and CPU VCC, and the actual measurement is 0 V.

EMB-6011 motherboard does not show maintenance when it is turned on Figure 7.

Repair CPU VCC, this board CPU VCC chip NCP81102M.

EMB-6011 motherboard does not show maintenance when it is turned on Figure 8.

According to the drawing, 2PIN is chip VCC 5V, and the measured 4.82V is normal. 2 pin 2V is pulled up, and the measured value is normal. 1 pin is turned on by ALL_SYS_PWRGD and SLP_S3#, and the measured value of 3.3V is also normal.

EMB-6011 motherboard does not show maintenance when it is turned on Figure 9.

Measure the wave-free type of the upper tube G with an oscilloscope, indicating that the chip is not working. Replace the good chip, and the fault remains the same after power-on. Re-measure the working conditions of the chip.

EMB-6011 motherboard does not show maintenance when it is turned on Figure 10.

When the equivalent reaches DRVON, it is found that the chip is turned on and the ground diode value is only 30, which is abnormal. The CPU of this board has 4-phase VCC, four identical chips in total, and the resistors are disconnected one by one according to the drawing.

EMB-6011 motherboard does not show maintenance when it is turned on Figure 11.

When it is disconnected to PR111, the diode value of other grounding points returns to normal. Measure whether the diode value of PU9 terminal is more than 30. After replacement, measure the ground value, and all diode value have recovered to more than 400. After changing the chip, power on, CPU VCC comes out, and the wave type of the front end of CPU VCC.