HP 400 G3 do not post but power is on

[Tuntematon]

I wrote this same question to spiceworks.com but the problem is not solved and I wonder if HP forum could help me out with this problem.

Link to thread in spiceworks 

So, I have this old war horse HP Prodesk 400 G3 SFF. It has worked fine for years but on friday it did not post. Warranty ended 2018 and therefore I need to ask this here. When I press power button the led light up but nothing more happens. No monitor signal (tested with several monitors). I have done all the tricks and nothing helps.

Please read the rest from the link above.

Anyone have any idea how to resurrect this nice piece of hardware?

[DGroves]

the most likely items that can cause this are 

power supply

defective motherboard

both items can be found used on ebay, but i question if it's worthwhile to do so

it may be a better choice to simply replace the system with another G3 or perhaps the slightly newer G4

[Tuntematon]

PSU should be fine. I've tested this setup with another good PSU and with it this hw do exactly the same.

I suspect that there is something fishy with the MB but I cannot figure out what.

As stated in the spicework thread in my mind it is strange that this is kinda semi-alive. Never seen symptoms like this. If this would be totally dead I would just throw this to metal recycling trash pallet. What is strange the it seems to me that some bios checkups are run (because of beeps/blinks if memory is removed or processor has no power) but it do not post.

This is zero money worth old computer and I have other newer computers and I could just throw this one to trash but I am curious to find out what is wrong with this because of the symptoms. Power is on and pre-post checkups are run but not completed. BIOS messed up or real hw failure?

I am not going to invest into this a dime but only some time if could revive this. Just for interest. Anyone any ideas to try?

[Ulf_K]

Try re-seating CPU and memories. Also do the same for any expansion board...