Hey Cemetech-I'm not sure if this is an appropriate thing to ask on the forums, but I've had a very large computer issue earlier today, and am unsure of how to proceed. I'm not here for tech support, as there are better places to do that-simply asking if anyone has ever encountered a similar issue and if it was solvable. I've also created a topic (that this is mostly copied from) on the HP Support Forums, but given that there are no replies yet, and that the majority of topics don't seem to receive any, I'm not counting on a response there.

System Specifications
HP Pavilion 16t-a000
i7-10750h
GTX 1660ti Max-Q
2 x 8 GB G.Skill Ripjaws DDR4 RAM (aftermarket)
500 GB Western Digital Black SN750 SSD (aftermarket)
1 TB HDD

Problem
When attempting to boot, the computer either gives a black screen or what appears to be memory corruption (possibly of VRAM, randomly colored pixels throughout the screen). Occasionally, I'll be able to get it to boot to Manjaro KDE (my OS), around 1 time in 30 or 40. However, when using the operating system, the problem will return, with the screen becoming corrupted/shifted and all input freezing. The BIOS is inaccessible most of the time, with the screen becoming corrupted or the Caps Lock key flashing before it can be accessed as explained below.

Diagnosis
The Caps Lock key gives three long followed by two short blinks, which according to this article suggests that "the embedded controller times out waiting for BIOS to return from memory initialization," or possibly a general system board failure.

Attempted Solutions
As my computer does not have a removable battery, I followed the suggested protocol (by the HP Virtual Agent) of disconnecting the AC adapter and all connected peripherals, holding the power button for 15 seconds, and then reconnecting the AC adapter and powering back on. I also took the computer apart, removing each of my 2 RAM sticks one at a time, as well as testing with an extra 4 GB RAM stick that the computer originally came shipped with. Using the HP Hardware Diagnostics UEFI, I ran processor, memory, and system board tests, all of which passed. None of these solutions appeared to help.
EDIT: Also tried holding the power button for 30, 60, and 120 seconds, and holding both Super+B and Super+V at boot, but none of these solutions worked either.

Image
Here's a general idea of what happens, captured from within the BIOS (the issue appears to be universal-it's happened within the OS as well). This is very rare, however: I usually can't even get into the BIOS or the OS at all. The colored lines and pixels do change in pattern, which would be kind of cool to watch if it wasn't my computer.


Conclusion/Warranty Information
This product is out of warranty (I purchased it in August 2020 for around $900 to my recollection, not including the extra hardware I got for it), which appears to mean that it is no longer eligible for official HP support. With that said, if that matters at all, I've always been careful with it, keeping it in a case when I go to school, and I've never dropped it. Is there anything that I can do to fix it, or do I have to buy a new computer? Thanks for all of your help in advance (again, just looking for very general tips if you have any). And mods-please remove the topic or give me a warning if this isn't something that should be posted on Cemetech.

Given the problem is intermittent, I'd think this is a (or more than one) bad solder joint somewhere on your mainboard. A cracked solder ball or something like that could reasonably work sometimes (those rare times that it boots) but also respond to heating by shifting slightly and failing again, and if it's on a critical signal (perhaps a memory bus) that could easily cause complete system failure or extreme display corruption.

A possible repair in such a case could be to heat the board in an oven to try to remelt any bad connections (like is fairly well-documented for GPUs), but it might be challenging to avoid damaging some of the more heat-sensitive components on the board such as connectors.

Update on this-thanks to Zeroko, DrDnar, tr1p1ea, Tari, and others, I was able to reset the CMOS on the laptop after trying some other solutions (pull the internal battery for 30 minutes, then put it back in and restart). After resetting the CMOS, the laptop is mostly working again, besides the fact that the screen is constantly flickering and still has some mild graphical corruption. With that said, everything is readable and thanks to the power of sensory adaptation I'm unlikely to notice the flickering after some period of time using the computer (and it isn't present while using an external monitor).

So, the computer lives! Thanks to everyone for your help, I'm really glad that I don't have to get something new while this one still works, or to try to bake the computer (although that was a good guess, thanks Tari).

Out of curiosity, do you have an external monitor to test on it? Try unplugging the LCD ribbon entirely from the motherboard and use an external monitor to see the OS, you won't be able to see the BIOS because of how HP laptops work (which kinda makes sense since your laptop should have a functional screen, but it really should be a thing on later models for debugging). If it still gives you weird stuff then the GPU is doing a thing, if there's a way to force the iGPU then give that a shot as well, if it works then at least you have stable video.

Well, as Tari predicted, the problem has returned-it took me around 10 tries to get the computer to boot so I could write this, and I've had it fail on me during use around 4-5 times in the last few days (though not at school, thankfully). As this is true, I don't feel like I can reasonably trust the computer anymore to be functional when I need it to. Additionally, I don't have the kind of technical confidence to attempt putting it in the oven, and don't think it would be worth it to replace the entire system board.

I think that I should replace it, what are all of your thoughts? This, luckily, would be a pretty good time to do that as well, considering that Black Friday is just around the corner.

EDIT-I've added a poll to the first post, please give a vote there if you have time.

I did some googling and found that the motherboard for your model is the M02033-001 and isn't sold on the HP parts store. Poking around found me some prices on other sites for under $600 US dollars, but some places list used versions for the same price. You could replace the motherboard, but two things might happen: it's a refurbished board and your OS might not like the new serial numbers for a little while, or it'll be fresh from HP in manufacturer mode, which means you have to boot up the PC and enter the exact serial, SKU, and CT numbers. That's unlikely though so a refurbished machine should be fine since all it's numbers will be populated, albeit slightly different. I originally voted to replace the part, but honestly replacing the whole thing would probably be easier. If you can't find a better deal, get a new machine. Did you try the external monitor though? It'd be a good way to test if the LCD is broken as well as the board if they're both causing separate problems. Oh, and remember to boot up the machine one more time to disable drive encryption if you have it or you'll lose everything. Good luck!

Quick update on this-I tried the external monitor fix, which resulted in heavy graphical corruption (though only on the external monitor, interestingly-I tried it both with and without the LCD ribbon cable connected). Following that, I completely uninstalled all of my NVIDIA drivers, and things seem to be momentarily working fine on the integrated GPU-there isn't any graphical corruption on either monitor, and the system boots up fine as well.

Again, things have been very intermittently working (as Tari predicted initially), so I somewhat doubt that this solution will persist for any reasonable length of time, though it would be nice if it would. I'll just disconnect the ribbon cable again and use it to do my homework to see if I run into any more issues, and if I do, I think it's pretty fair to assume the issue is with the motherboard, rather than simply a graphical problem.

And last thing here-where are you finding these motherboards? This is essentially the only one that I could find with that model number, and it has a lower specced GPU and CPU (i5-10300h + GTX 1650 vs i7-10750h + GTX 1660ti) for slightly over $850, which is basically the same price that I paid for the original system. With that said, thanks for taking the time to do that research. That information is very useful.

So, final verdict is that it's again working, though this time without the dGPU and only using an external monitor (?). I'll update as I have more information. Hopefully I'll have made a final verdict on it by this Friday, as I'd really hate to miss Black Friday if I do have to replace the computer.

The SN I found was for a lower version, that's my mistake, but here's how I got the right one. First I went to HP partsurfer, but without a serial number I couldn't get an exact part number. I found the part locator manual on HP's site, and while the board is too blurry to make out a number, I at least knew it looked like a ping-pong paddle. I googled around looking for similar boards and found your model but with a 1650 on Aliexpress. I wanted to find a cheaper board, so I decided to try to find some disassembly videos with the mobo exposed. The CT number is under the RAM so I had to find some high-quality RAM upgrade footage, which wasn't that hard. It's blurry, but it looks like M02036-001 and parts.hp.com lists it with your exact specs. Sadly, HP doesn't sell it or any of it's variants. Googling it turns up various mentions of it but no resellers. Could you check for a board revision and a serial number on your mobo just to be sure?

Another update-the system failed on integrated graphics multiple times at school today, meaning that it's not the GPU. Also, that same system board code came up again, which seems to suggest that it is the issue.

And thanks, KingDubDub! I'll get you the information on the board tomorrow if I have time, but I think that I'm just going to replace it at this point.

EDIT: I did just purchase a new computer, the ROG Zephyrus G15 in the Ryzen 9 5900HS/RTX 3070 configuration thanks to an incredible Best Buy sale (bought open-box excellent). I still may reconsider that, and I'd still rather not spend that much money, so I'll give a last attempt at diagnosing/fixing the computer tomorrow.