The customer brought a Lenovo brand machine and said it was not turned on.
Get the hand power, do not trigger, measure the power supply, USB to the ground.
Seeing that the motherboard BIOS has been moved, I thought it was a small problem, but it was useless to discharge and brush the BIOS. There’s no way out. Remove the power supply from the side.
There are 12v, 3.3 and 5v, and that’s the problem.
There was no en in the test, but there was 3.3, and there should be 5 V. He just couldn’t find it. He read another big boss’s post.
The triangle tube on the left side of PC920 is controlled by en. If it is removed, it still won’t work. I planned to change the power supply IC, went to Taobao and asked Mr. Su, and the result was 25, which scared me to decide to remove it on the spot.
How about measuring the resistance of each foot? The resistance of G turns out to be 45, which is the same as that of S, so I understand. G passes S, after replacement. Exquisite, when I entered the system, I found that six USB could not be used.
Measure the safety tube 5 pin tube. One end is 5v and the other end is not, u54 u51
Take it down and connect it with tin wire. Don’t ask why you don’t replace it. Next time you burn it, it won’t be a big piece, just like the safety resistor O ohm.
Re-enter the system and solve it perfectly.
Therefore, be sure to ask about the customer’s use, phenomenon and recent operation, or you will take a lot of detours.
Also, don’t believe everything the customer says, burn USB at 12 V.
