Dell Latitude 5520 completely dead

[diamon]

I have bought a not complete and defective Dell Latitude 5520 for parts (needed the networkconnector (RJ45) to repair a other board).
Have repaired the other board (Dell Latitude 5540) and I wanted to know if I could find out what is wrong with the 5520 board (SouthPeak15 TGL MB 8L 19819-1) and perhaps repair this one also.

After connecting the USB-C charger (both USB-C ports on the laptop, does not have an other option) and pressing the power button, nothing happens (no lights or fans, no capslock).
Have checked with a thermal camera, and there are a couple of things getting hot (glowing):
DC-IN mosfet Q7408 (the other 3 staying cold)
PU4501 > creates the 3.3Volt
U2401 > mec5107

I have replaced the Q7408, but no differences.
The power button has 2,4V and with pressing the power button it is changing to 0V.
The mec5107 is getting 3.3V, don't think the issue is the chip creating to 3.3V.

According to my knowledge, the issue is a shorted mec5107 chip. I have checked the schematic of this board, these schematics are to complex for me to fully understand).
I'm I correct that the mec5107 is the issue?

I have attached some pictures and the boardview and schematic of this board.

The schematic is here: https://www.badcaps.net/forum/troubl...73#post1798173
The boardview is here: https://www.badcaps.net/forum/troubl...00#post1873600

[mon2]

Locate the RTC battery connector @ connector RTC1. Measure the voltage to ground of pin #1 on this connector = +RTC_PWR. What is the voltage? This voltage may be low and with the voltage drop through the diode @ Q2501, the voltage on the power button is 2v4. Suggest to replace the battery with a fresh one and test again.

[Lister7]

You find somewhone...

Mine Latitude 5520 doen't start; he can't find the TPM--cu

It shows 1 time white Light in Front

[reformatt]

I've just fixed one of these this week. It was power cycling up to Vcore for around 10 secs then resetting. Fault was a corrupted BIOS; booted fine when this was corrected by reflashing U2502.

However, and my reason for posting, this board won't boot with only USB-C connected, and needed the battery connected for it to start. I wasn't using a original Dell USB-C adaptor - with only a 90W Apple charger connected, RUN_ON_EC would not be asserted. But with battery, it would boot, show it was a 90W charger and also charge the battery. This model can take 65W, 90W and 135W chargers - perhaps it needs an OEM 135W charger for it to start without battery. Typical Dell BS.

Very unlikely to be your MEC. If it was shorted, you wouldn't have your LDO 3.3V.

[Lister7]

The Boardbattery has more than 3 volt. The Akku and original Dell USB-C Adapter are ordered. See more when it come..Thanks

[Lister7]

The second board only receives 5 volts; the PU4501 chip next to the battery connector and the coil gets over 90°C hot and won't start...