Dell XPS 9500/Precision 5550 - random freeze and no post + display glitches

[TheQuentincc]

Hi, I have a Dell XPS 9500 which works when it want. Specs : I7 10750H, GTX 1650Ti 4GB, 15.6" 1920x1200.

It can works fine for hours until the screen goes black or the image is fully frozen (laptop unresponsive) or the display is glitched.
Then another issue is sometime the laptop doesn't wanna boot or post at all, after a "clear cmos" (disconnecting main battery and pressing power button for some time) when I'm pressing the power button the keyboard lit up but sometime the laptop display the Dell logo, sometime the screen can just lit black, sometime it launch the RGB panel testing, sometime it just makes the fan spinning at 100% then shutdown...
During this I got no feedback on the activity LED, it's just white and doesn't blink... the craziest thing that did happenned to me is the Dell logo showing up while there was no memory/DDR4 installed...

I tried flashing the lastest bios using Dell software which indicated the ME corporate firmware was missing (the consumer one was present), I don't know if it's supposed to be present or not but the update was successful (meaning no errors).

Then I booted Windows, was playing music and decided to check temperature using hwinfo, as soon as I launched it I had this screen flickering (see attachment), I tried touching a bit the display cable and it did nothing, I had no choice than forcing reboot because the laptop was unresponsive.
When hwinfo is running I believe it does wake up the dGPU... So thinking it might have been related to the GTX 1650Ti (even though it's the Intel UHD that does output the video), I disabled it in the device manager (I got the laptop to boot again after a few clear cmos)

While I was mem-testing the main memory (I thought DDR4 2933MHz might have been a bit much for the CPU to handle) with OCCT I was messing around with throttlestop and power limit (for fun), then I touched the display and everything froze (I had a music running in the background but it stopped).
I tried playing with the display and ended up to this artifacts while the laptop was completly froze :
https://youtu.be/R5K-uf8WVGk

So far that's pretty much where I am right now... I believe the display flex cable is the main culprit BUT I don't understand why it does prevent the laptop from sometime booting fine and sometime not, also I highly doubt the bios/EC firmware are bad at the same time as the display flex cable...

Does anyone got an idea ?
Thanks you all for reading

[FZG]

Re: Dell XPS 9500/Precision 5550 - random freeze and no post + display glitches

Did you try to output the video to an external monitor simultaneously? Just to see if the artifacting shows up on external display as well. If it does show up it´s not the display cable but rather a faulty GPU or VRAM issues.

[TheQuentincc]

Re: Dell XPS 9500/Precision 5550 - random freeze and no post + display glitches

I did not tried since I do not have such adapter but the laptop was unresponsive (no action when pressing the power button), so using an external display wouldn't change much I believe.
But a faulty GPU/VRAM issues is pretty unlikely as the system doesn't use it for video output (it's the Intel UHD doing the work) and it was disabled when it happened :/
I dumped the full 32MB bios/EC chip, can anyone have a look and check if it's corrupted or not ?
Thanks you all

MOD Edit: Bios deleted. Bios requests go here -> https://www.badcaps.net/forum/forumdisplay.php?f=40

Reminder, rules and organization of this section -> https://www.badcaps.net/forum/showthread.php?t=117483
.

[FZG]

Re: Dell XPS 9500/Precision 5550 - random freeze and no post + display glitches

I doubt the BIOS is corrupted if the device starts at all.

The picture you posted here and the description of freezing symptoms looks like RAM issues to me. The video you posted on Youtube seems to hint at a broken display cable. So you should focus on these things first.

When you have the device opened and running, try wiggling the display cable (most likely spot for a break is in the hinge region).

I would also try to eliminate RAM issues by testing with a known good RAM stick. Memory testing in OCCT or any other program is fine but it does not mean much.

[TheQuentincc]

Re: Dell XPS 9500/Precision 5550 - random freeze and no post + display glitches

I already tried 2 other memory kits from other daily laptop ranging from 2666 to 2933MHz SPD.
I believe there is something wrong with the EC since the laptop isn't always giving a blinking error code when something is wrong at post.
For instance sometime I don't have an error code when it's failing to post (keyboard is lit, fan at 100% then shutdown) and I'm not even getting an error code when there is no ram installed.
And that's why I dumped the bios chip, to make sure the EC and bios are good before trying to replace the display cable or whatever because it's pretty hard on theses display (they are glued and hard to teardown without breaking compared to other laptop)

[TheQuentincc]

I think I finally found the issue, I had replaced the GPU core and tried to reflow the chipset but it didn't helped. Then I investigated and found the VCCIO power plane (PL800) that wasn't giving power when the EN signal was present... I replaced the mosfet and now it's working fine.
For the record when it was stuck on the Dell logo there was no VCCIO power... what a weird thing to do when a power plane is missing, my theory was that every voltage were fine since it was displaying something, I was wrong.
The mosfet to replace is a NB681AGD-Z, I just grabbed one from my Precision 7550 motherboard.
I guess it was sometime working and sometime not, hence the crash/artefacts when I was using it.

(if a mod see this post, could you please edit the title and add a "FIXED" at the beginning so it could help other ? Thanks)