Dell 15-3543 alarm four suspected common fault repair

Dell 15-3543 alarm four times, suspected common failing, changed the screen and Fuse, the fault is still the same, continue to measure found that Fuse power, so directly on the main board f5201 Jump wire fly to Fuse, fault repair.

Machine model: Dell 15-3543

Machine plate No.: 13269-1

Fault phenomenon: the machine alarm four times, the fault is heavy

Maintenance process: get the machine and find that it is powered up to 0.8, then auto power off to 0.45 or so.Then he began to dismantle the machine. He found that there was some water damage in the memory. He thought that the memory might be broken. If the memory was broken, it would be difficult to quote the price. Then he took down the machine with a nervous heart. After dismantling, he found that the main board had no obvious trace of water damage.Then, the memory is replaced first, and then there is no result. After that, I wonder if there is something wrong with the motherboard. Then I measure the wlan1 22 pin pltrst ා on the mainboard, and it is found that there is a plaorm reset.

Dell 15-3543 alarm four suspected common fault repair Figure 1.

Then I thought that this might be a memory problem, and then I went to do a set of procedures, put the CMOS battery VCC fruitless, brush BIOS, clean the memory interface.Clean the memory golden finger, fruitless, and then measure and memory SPD found to have, and then to measure memory VCC chip tps51716.

Dell 15-3543 alarm four suspected common fault repair Figure 2.
Then the measurement found that 1.35v is normal and 0.65v is normal. This is really strange. The memory was changed, BIOS was swiped, and the memory slot was wiped (three rhyming). I don’t know how to repair this pin. Then I went to the forum and found that there were posts in this area saying that the common failing CPU was broken (link here)https://www.chinafix.com/thread-1271644-1-1.html）In the post, the problem of memory reset VCC was mentioned. Then I went to measure the memory reset VCC on my machine. As expected, the reset VCC was not 0.11v as I expected.

Dell 15-3543 alarm four suspected common fault repair Figure 3.
The CPU is broken, the CPU pulled down the VCC. Originally, I still thought that the memory was broken and the quotation was not good. Now it’s better that you don’t need to quote (generally, the customer can’t accept the change of CPU). Then, holding the dead horse as a living horse doctor, he directly used copper wire short-circuit for r410, then plugged in and started the machine.It’s still not easy to light up the screen, and then run up.But now it’s not going to call the police.Later, I found that the screen would flash when I started up. I thought it would be dark. If I use a flashlight, it would be dark. I wonder if there is any problem with the main board screen circuit?Then measure the backlight condition of the screen VCC 19v, and some backlight EN.

Dell 15-3543 alarm four suspected common fault repair Figure 4.

Dell 15-3543 alarm four suspected common fault repair Figure 5.
And then change a screen to kill it easily.Then we took apart the optical circuit in the screen measurement meter and found a Capacitor Short circuit. After dismantling, the Fuse in front of it was also hung up. We replaced it directly. Then we thought it would be easy to kill in seconds. Unexpectedly, the fault still remained after it was installed.Then continue the measurement and found that Fuse is out of power, and the measurement screen interface 29 pin has 19v. Then I feel that the interface of the second screen is not good Jump wire, I directly fly to Fuse on the f5201 on the motherboard, and then plug in the power again, turn on the machine, and the screen will light up easily!