Lenovo B40-30 Laptop Does Not Turn On Repair

Laptop Model : Lenovo B40-30

Motherboard Number : LA-B092

Fault : Does Not Turned On

 

Repair Process:

After taking it apart, it was found that there was water in many places.

These are some of the more serious pictures I took at that time. There are many other things that are not so serious. I don’t have too much hope.

 If the client agrees to the repair, let’s deal with it first! Clean it first, replace all the moldy and damaged ones, and measure the resistance and find that the 5V power supply is connected to ground 0.

I disconnected the PJ402 node (this node paved the way for my subsequent maintenance process) and found that the front stage was short-circuited.

When the Laptop burned, I found that the power supply chip was hot. I removed the chip and measured the resistance value, which returned to normal. I found this chip from the drawing. 8208, order.

When the chip arrived, it was replaced and the resistance value was normal. When powered on, 35V and in standby came out, but it didn't trigger? So I thought that the EC had also entered water, and whether the EC had also failed, and went to test the EC conditions.

Power supply 3.3 is normal, REMRST# is normal, EC_ON is normal, EC_RST# is normal. When PWRBTN is measured, it is found that there is no jump.

I checked the BIOS again before setting the EC, but it is still the same. When the EC arrives and is replaced, the 3V and 5V are gone. , this EC comes with a program, and I bought a shearing board.

It was my first time to switch to EC, and I felt a little nervous. I thought there was nothing I could do, so I decided to reorder it! Before resetting, I went to check the entire motherboard again.

This inspection found the problem. When I repaired the 5V power supply, PJ402 was disconnected and I did not connect it. In this way, it is possible that my original EC was not broken, so I did another operation to restore the original EC.

　　After powering on, the 3V and 5V standby functions were still not triggered. Later, I thought that the BIOS had been manipulated by me, so I reset the original BIOS. After powering on, it finally turned on.

All the subsequent work was useless. The 5V power supply chip should have failed before, but I changed the chip and forgot to add it to the PJ402 node, which resulted in a series of useless operations.

Happy Repairing !!