Dell T7910 Refuses to post even after replacing every component.

If not already, start by testing or replacing the size 2032 CMOS battery.  Even if the extra MB's came with batteries, sellers never make sure they're any good.

A bad battery affects BIOS and therefore PC operation.

@bradthetechnut​ I just ordered some more to test with, I checked them though and they all read above 3v. Would a bad CMOS really hang the bios like that? I've never experienced that on any other platform.

Not every component was replaced.  The GTX 1050Ti is getting a little old, and sometimes they fail, though not often.  I doubt it's the RAID card since you get a green light,  but it would be next.

@bradthetechnut​ 1050ti is my testing card and I verified its function on a different computer about 3 times during testing. Raid controller is built into the Motherboards so it's been replaced twice too. Every component has been replaced except the power connector wires but those trace out fine. I even swapped it into a different case in case that was the issue. 

"Would a bad CMOS really hang the bios like that?"  Yes.  When I had a bad battery in my Precision 3620 and tried ignoring it for a while, at first it would freeze a few times.  Then it went BSOD and it's recovery options didn't work.  Then I unnecessarily tried reloading Win10.  That wouldn't work either.  So I replaced the battery and reset BIOS.  Then I had to finish reloading since I already started it.

Try resetting BIOS via the blue jumper method.

Time to do a fresh install.  You never said if boot drives were replaced or not or their status.  Replacing and starting totally fresh isn't a bad idea.

Download Win11 from the Microsoft site.  Use an 8GB or larger flash drive formatted to FAT32.  They often come that way anyway.  Your PC is from 2014 and isn't on the supported list for Win11.  Microsoft site Win10  Microsoft site download Win10 ISO (recommended)

You'll probably need to inject a driver upon reload.  @Chino de Oro knows what driver that is or how to find it.

Lastly, one idea is to put all the original components back and return the thing.  I hope the 7910 came with something for a return policy.

For loading or reloading OS, BIOS should be set to AHCI or RAID and Secure Boot On.

@bradthetechnut​ New Cmos arrived, has not helped on any of the motherboards. Bios reset via jumper has been tested quite a few times but I just did again with no change. There is no boot drive installed when I do these tests other than when I installed a known working windows instillation and I also tried an ubuntu server pre setup on another machine to open a ssh server. Ssh server never opens. OS shouldn't matter though as it never even gets to initialize HIDs let alone Pcie busses or BIOS. No return policy sadly or I would've thrown in the towel long ago. Now I can't even be comfortable parting it out because I can't tell what's wrong with it. Physically there should be no issues but still doesn't post which is what's making me scratch my head.

So you can't even load/reload OS?  what driver needs to be injected into flash drive for loading operating system on a Precision t7910

@bradthetechnut​ No sadly this is not an issue on the OS level this is rather a hardware/ Post and bios level. There is either something going wrong in the power on self test or something going wrong In the bios that stops the boot from continuing. No drives are initialized, Usb never begins communicating and neither do the PCIE lanes. It never gets into the bios or I would be able to see life on the keyboard like caps lock or an output from the gpu. Unless dells are different from every other platform i've ever worked on. Thank you again for the help.

the issue is that you tried with different motherboards and different cpu, and the chances you got all those defective are very low. Is there anything you kept using during the various tests ?.

Did you install the mb always inside the chassis before testing + connecting the front usb ? If yes, disconnect the front usb cable, in case there's a short in the external connector @user_f63187 

@mazzinia_ @bradthetechnut Taking a crack at this again because its been sitting around for months now and I wanna make sure its dead before dumpstering it. I have now completely removed everything from the case and am running it bare on my workbench (with a silicone mat under it). The only things connected are the 3 power supply headers, jumper wires to the remote power switch to start it and the intrusion switch that is held down with tape(and I've tested without). I have hooked an oscilloscope up to the rails of the power supply and don't see anything happening on there. I have also tested each wire individually and it all seems fine. I am still getting the same results sadly.

Thanks again!

@user_f63187​ sad to hear. So on a bench ... the psu looks fine ... mm

Have you considered trying to bypass entirely the intrusion detection switch ( lets imagine is faulty and tape or not, is not closing the contacts ) ?

@mazzinia_​ I tried jumpering it and it didn't work I tested continuity with a multimeter and it seems to open and close fine. 

@user_f63187​  this one has been a really weird issue... I mean, I reread and you changed motherboard, cpu , ram , even tried a different psu and the issue kept identical

now is stripped on a bench, excluding the case from the equation... only thing that seems be the same as before would be the power button harness ...

@mazzinia_​ I have removed the power button harness for the last few tests I'm using a separate button across the "remote pwr" pins on the motherboard. At this point I might just chalk this up to several bad batches of parts. It makes absolutely no sense that it is still not working unless there was a short or something that fried each new component I installed the second I ran the first test with it.