Laptop doesn't power on after motherboard replacement/gpu is not recognized or visible

[sagaidak.m]

Hello everybody.
I have a 6-year old laptop hp envy 17-3090nr which overall works fine. This model had two almost identical series 30xx and 32xx - the latter was slightly newer and thus more powerful. So I decided to make an upgrade - ordered motherboard from 32xx series (this one - https/www.ebay.com/itm/173204381540?ul_noapp=true) and new CPU (i7 3840qm from Aliexpress). Although the most powerful CPU that was put in these laptops was 3820qm, I chose 3840 as the most powerful supported by motherboard chip hm76 (http/www.cpu-upgrade.com/mb-Intel_(chipsets)/HM76_Express.html) - it wasn't on the market at the time envy were produced but I don't see any significant difference between 3840 and 3820 that should prevent it from working.

So yesterday I've assembled laptop with new MB and CPU and it didn't started. Actually something was happening - fans were running for a second but then full stop - just several lids continuously lightning indicating some error. Also sometimes when I tried to power it on - some weird echoing noise has appeared from speakers for several seconds.
After some google I've tried in several useless combinations:
-unplugging CMOS battery from MB,
-holding power button for 30 seconds.
-unplugging RAM

So from what it visible now:
-motherboard is powered - lids are lightning and it tries to power on but immediately stops,
-motherboard is bought from good-rated US seller ftg parts - so in general I assume it should be in a good work condition.

Can it be the CPU that stops the laptop from powering on? Is it MB/CPU incompatibility? Or broken CPU? Or is it possible to install CPU incorrectly (of course I have aligned according to the direction mark and locked in CPU holder)?

Also what kind of diagnostic can help to find out the cause of the problem?

Please advice would it be helpful to attach a video of symptoms occurring when trying to power it on?

 

[Lutfij]

I'd ask you to use one stick of ram and then try powering up. This single stick of ram can go be placed in slots 1 or 2 and vice versa. See if that helps. If you yet have the older processor(which you haven't mentioned) then try dropping it into the new board and see if that boots up.

I often suggest that you run with bare minimums just to gain BIOS functionality. From there you can see if the board needs a BIOS update. Once on the latest BIOS update, you can try and drop in the new CPU and see if that works for you.

Your processor should be supported according to this chart:
http/www.cpu-upgrade.com/mb-Intel_(chipsets)/HM76_Express.html

 

[sagaidak.m]

I'd ask you to use one stick of ram and then try powering up. This single stick of ram can go be placed in slots 1 or 2 and vice versa. See if that helps. If you yet have the older processor(which you haven't mentioned) then try dropping it into the new board and see if that boots up.

I often suggest that you run with bare minimums just to gain BIOS functionality. From there you can see if the board needs a BIOS update. Once on the latest BIOS update, you can try and drop in the new CPU and see if that works for you.

Your processor should be supported according to this chart:
http/www.cpu-upgrade.com/mb-Intel_(chipsets)/HM76_Express.html

Thank you for your answer.
I've tried with different RAM combinations, even without any RAM - didn't produce effect.
Regarding CPU - it is possible to try. The old one is i7 2670qm . It is not in the list of supported by hm76 - but some googling shows that some people used it in such combination.
I'll try CPU replacement tomorrow. Also - is it necessary to apply thermal paste just to see if the laptop powers on?

 

[sagaidak.m]

Here is what I found out so far.
Laptop start if additional block of USBs is disconnected from motherboard. There are a couple of USBs, headphones and microphone plugs.
But after several minutes laptop turns off. CPU and gpu temps are OK. But motherboard chipset seems to be heating a lot with no reason. Also after it turns off then it can try to turn on several times.
Can it be some BIOS issues?

 

[sagaidak.m]

One more update. I've managed to load the system and update bios. But apart from preventing constant shut downs it didn't bring other desired effect. For example laptop doesn't see gpu not in windows device manager nor in bios. Moreover in bios laptop is recognized as some old hp pavilion dv3 with a serial number 1234567. Tried several bios versions - didn't help