Lenovo E575 boot display is normal, computer flash screen common fault repair

Lenovo E575 boot display is normal, computer flash screen common fault repair

Machine model: Lenovo E575

Fault phenomenon: computer flash screen

Lenovo E575 boot shows the normal computer splash screen, the screen flashes, the external connection does not flash normally, and the version number is shown in the following figure.

Lenovo E575 boot display is normal, computer flash screen common fault repair Figure 1.

Lenovo E575 boot display is normal, computer flash screen common fault repair Figure 2.

Change the screen directly, the fault is still the same, there is not much measurement, and it is suspected that there is something wrong with the screen line. I ordered the screen line, but it still didn’t work. Search forum found a similar case to be solved by brushing BIOS, but it is still the same after brushing, measuring the screen interface signal.

Lenovo E575 boot display is normal, computer flash screen common fault repair Figure 3.

+LEDVDD 12.2V should be normal, common point 12v,+LCD vdd _ con,+3vs _ CMOS,+3vs VCC is normal, APU_EDP_PWM brightness level 3.12V is normal, BKOFF# is abnormal at one o’clock, two o’clock and three o’clock. Check the source from EC IT8586E/FX LQFP, so either the program is bad or EC itself is bad.

With this EC chip, R809H can brush it, but I can’t brush it only with R809F, so I can only buy the board cutting chip. Considering the time and cost, the EN was disconnected directly, and then the +LCDVDD_CON 3.3V screen did not flash. Later, the test found that the machine would automatically screen is black or frozen from time to time, and then it would light up itself after a while.

It is estimated that FB will be sent to EC or other signals will affect EN. If it is disconnected, it will not work. It is necessary to change the EC, order a shear board, and in a few days, it will still be the same.

Lenovo E575 boot display is normal, computer flash screen common fault repair Figure 4.

Later, at Tanyou’s suggestion to measure the sleep signal,VCC is normally 3.3V, but the actual measurement of VCC is a little more than 1 o’clock, which is abnormal. Check the drawings and find it here.

Lenovo E575 boot display is normal, computer flash screen common fault repair Figure 5.

This is the removed picture. It’s already a little Oxygenation corroded by moisture. The removed screen shows that it is normal, and the maintenance is over.

The abnormal sleep signal affects EN,VCC current of change, and the screen turns on and off splash screen.