A1708 (820-00840-A) - no image

[alexnavin_]

Hello there
There is no image. Before me, someone disassembled and damaged the trackpad cable, I measured it and did not find a short circuit in it. When turned on, all voltages are present. The fan starts only once for a few seconds and stops, while even with strong heat it does not turn on to cool the processor. If you unplug the trackpad cable and turn on the laptop, the fan starts immediately and gradually picks up maximum speed. There is no sound from the speakers. A couple of times, after several switching on and off, he still showed an image, and I moved the lid to understand if there was a problem in the matrix cable or not. I did not notice any artifacts and image distortions, so the problem is not in the matrix cable. In the photo, I indicated what voltages are present on the board. When the laptop showed the image, all voltages were the same as I indicated in the photo. Please tell me what the problem is.

Spoiler: Photo

 

[alexnavin_]

When the charger is connected, the tester shows + 20V, and the consumed current is about 1.5 A.

 

[2informaticos]

First of all, welcome to the forum!

Start telling us 820-008xx code of your board.
Do you still get 0.6V on CPU core, when no image present?
Did you check external video and USB activiy?

Replace trackpad cable.

 

[alexnavin_]

Code of my board is 820-00840-A.
At the moment + 0.96V on CPU core, and the laptop restarts if it is running on battery power only. It works for 10 seconds, turns off and after 5 seconds turns on again, and so on endlessly. If you connect the charger, the laptop does not reboot, the CPU voltage is still + 0.96V. Unfortunately, there is no way to check the external video, there is no adapter, I recently ordered it. Please explain how to check the USB activity?
Will a laptop work without a trackpad? I would like to fix my laptop first before ordering a trackpad cable.
Thank you.

 

[alexnavin_]

When the laptop showed an image, the trackpad cable was connected.

 

[2informaticos]

TP cable must be changed anyway, as it is damaged.
Without it, the machine will get slow and fan spins to max; embedded temp sensors are not detected.

"At the moment + 0.96V on CPU core"
You've posted 0.63V in the first post (L7210/20).
With 0.96V board can stay on, but doesn't really boot.

 

[alexnavin_]

Thank you. Do you mean that the problem is still with the matrix cable? My friend has exactly the same laptop, he will give it to me today so that I can connect my board to it. This way I will determine what the problem is. Am I doing everything right?

 

[alexnavin_]

You've posted 0.63V in the first post (L7210/20)

At first it was, but after he showed the image, the voltage also changed.

 

[alexnavin_]

I put a non-working board in a fully working laptop and its behavior has not changed. There is also no image. The voltages are the same. Then I put the fully working board into the non-working laptop and it turned on. Thus, I found out that the matrix cable is working, and the trackpad is also working. The battery showed 59% charge. Now we can conclude that the problem is precisely in the board. I compared the voltage of the CPU, and noticed that on the working board it is + 1.04V. I ask for help to diagnose it correctly and repair it. Thank you.

 

[2informaticos]

When board boots, voltage should drop to 0.6V aprox.
This value will change in time, depending by CPU load.
If stuck in 0.96V, board is not booted.

Test the board alone on the desk; no SSD, no trackpad, nor battery.
If board randomly booted before, there could be some corrosion, or bad solders.
You can try known good BIOS, just in case; already posted on the forum.

 

[alexnavin_]

I'll try to flash the BIOS. Do you mean this one?

820-00840 no video but backlight present

There are no signs of spillage on the board. I have tried reseating the video cable. The board draws 20v at 640ma. I dumped the bios but meinject tool says theres no me region or me region is corrupt. It make a sound when you plug it in and using a Chipmunk it flashes usb activity. Cpu Also gets...

boards.rossmanngroup.com

 

[2informaticos]

Yeah, both files from that thread should be good.

 

[alexnavin_]

After the firmware, the board's behavior has not changed ...
I used this dump - https://boards.rossmanngroup.com/threads/820-00840-no-video-but-backlight-present.61055/post-74370

 

[2informaticos]

Then put bak original BIOS.
There should be bad contacts/solder, or corrosion issues, if board randomly booted.
You can try to heat CPU with quality flux; only to burn eventually accumulated crap, no need to melt the balls.

 

[alexnavin_]

To what temperature should the processor be heated? 210-220 Celsius is this normal?

 

[2informaticos]

180-200 for 15-20s is good enough.
"no need to melt the balls"

 

[alexnavin_]

Ok i got you, thanks