Dell Inspiron 5370 - It doesn't always start up

[Nagyesz]

Hi everyone!

Unfortunately, I've been struggling with this laptop for a few days now, and although this isn't the first laptop I've repairing.

Out of 10 startups, the screen only comes on about 1 time. When it does, the laptop works perfectly and passes various tests. I've replaced the CMOS battery, RAM, RAM slot, and the charger (tried both 65W and 135W), but it's still unpredictable. When turned on, the Caps Lock light comes on and then shuts off with the laptop. Other times, it does boot, but it may take several restarts to do so. On one occasion, it started up immediately, even when laptop was cold.

I can't perform a BIOS update because there's no battery for the laptop, and it shuts down during the process. However, the screen does come on everytime I press the power button + "D" (BIST) mode)

What should I do now?

[Nagyesz]

Done with bios update, also reinstalled windows

The dell now always turns on, but it still shows the firmware update, although it stops at 0%, probably because of the battery again. I think I can handle it from here, thanks everyone.

[mon2]

When it shuts off, confirm that the DCin power adapter voltage is present on the motherboard. This is to rule out that the connector could be the factor.

Otherwise, remove all power. Remove the battery (if present). Measure the resistance (not diode mode) to ground of each inductor on the board. You are checking the resistance to check if there is a shorted part on the rail which will cause an excessive current draw and then will power down that rail. If you find a lower than normal resistance, then that rail is a suspect. Low voltage rails like the CPU will be with a low resistance to ground, by design.

[Nagyesz]

Thanks for the advice, Mon2! It have Dcin.

I measured all the inductors alongside it, the processor one is 4.4 ohms, 5V is 136 ohms, etc. Unfortunately, I don't have the boardview yet, but none of the lines seemed strange.

However, another symptom has appeared: the CPU fan doesn't spin. When the computer turns off, it spins a little, or if I unplug it while the computer is on, it runs for a few seconds when I plug it back in, and that's it (The processor was quite hot, and the cooler didn't do anything).
Also, I've tried the third Wi-Fi card now, and it still has issue. It doesn't want to recognize it.
Additionally, I adjusted a few settings in the BIOS, and now the computer starts after about 2-3 attempts when it's completely cold, taking about a minute and a half.
And sometimes it boots, but the screen remains black in Windows.

I'll manually reinstall the BIOS on the computer or by usb.

I think this will be the best option I can try right now.

[mon2]

5V is 136 ohms

This is too low. Review the USB 2.0 ports which will use the same rail for the VBUS pin(s). Confirm the resistance to ground.

It is possible that you have local USB load switches which are expected to turn off VBUS rail in case of a short circuit / excessive current draw. However, often, the USB load switches get killed. Check for any such suspects and if found, remove them off the board with flux and hot air tools. A defective load switch can cause this event.

[alfredposadas09]

Thanks for the advice, Mon2! It have Dcin.

I measured all the inductors alongside it, the processor one is 4.4 ohms, 5V is 136 ohms, etc. Unfortunately, I don't have the boardview yet, but none of the lines seemed strange.

However, another symptom has appeared: the CPU fan doesn't spin. When the computer turns off, it spins a little, or if I unplug it while the computer is on, it runs for a few seconds when I plug it back in, and that's it (The processor was quite hot, and the cooler didn't do anything).
Also, I've tried the third Wi-Fi card now, and it still has issue. It doesn't want to recognize it.
Additionally, I adjusted a few settings in the BIOS, and now the computer starts after about 2-3 attempts when it's completely cold, taking about a minute and a half.
And sometimes it boots, but the screen remains black in Windows.

I'll manually reinstall the BIOS on the computer or by usb.

I think this will be the best option I can try right now.

have you try to flash the bios or clean the me region?

[Nagyesz]

Just checked VBUS, and both usbs found nothing, both usb works correctly.

have you try to flash the bios or clean the me region?

Not yet, first I will try to flash bios by usb, then clean me region

Update: It turn on first try

[Nagyesz]

Done with bios update, also reinstalled windows

The dell now always turns on, but it still shows the firmware update, although it stops at 0%, probably because of the battery again. I think I can handle it from here, thanks everyone.