Computer not powering on, dead motherboard?

[jazzercise]

I have an HP Envy desktop about 5 years old. The computer doesn't get shutdown and is either being used or left in sleep/hibernate mode.

The computer doesn't power up at all, no case/button lights, fan activity, or anything. I tested the PSU with another computer and it is working and also another PSU in the Envy. I noticed when hooking up the PSUs on the Envy that when electricity/power cord is connected  and not connected to any components the green light on the back of the PSU is solid green. But if I connect it to the motherboard (24-pin?) the light on the PSU turns into a blinking green light. If I disconnect it and plug any other power cable (sata, molex, etc) the light stays solid. I also tested both PSUs in my older HP Desktop and when all connections are in, the light stays solid green.

If the light only turns blinking green when I plug it into the mobo does that mean I'll have to buy a new mobo/cpu or is there any possibility there is a more inexpensive fix?

Both PSUs tested are rated 300W.

[erico]

Your troubleshooting does indicate a possible failed motherboard, but could also be a failed memory module.

You can go a bit deeper by removing the memory modules and then connecting the PSU after putting one module in the DIMM slot closest to the processor.   Power the system up to see if the PSU LED stays solid green.  If not, power down and test the next module.

[jazzercise]

Unfortunately no luck with this method. Test both sticks and all slot permutations with single stick of memory. Thank you though. Seems like I'll have to start looking for a new machine.

[erico]

Ok.

It is a dead motherboard then.