I swapped my aging PSU for another, from 850 watts to 650w. Sale.
I wired it up, checked connection, and no power. I suppose one of the cables on the modular PSU were not tight, because after taking them out, and reconnecting them -- it powered up. I had no video, though.
I have taken all but my MOBO out and ran from the MOBO HDMI. I still have no video. I have also tried my OLD power supply and it does not work either.
I have rechecked this several times, ensured I had the proper cabling, and that was snuggly fitted. I have no idea what is going on at this point -- the only conclusion I have is that somehow the new PSU fried the MOBO?


 

no, the old PSU was not modular, so I had no option to even use them. So yes, I used the new cables with my power supply.
 
MB - ASUS 450 B Prime plus
Bios - no idea, unable to view them presently.
GPU - EVGA 2070 Super.
CPU - Ryzen 5600x
Ram - 16 gb ddr4 Corsair ram
windows 11.
 
Presently, I have nothing but the CPU and one stick of ram installed. 

1st thing: yes, latch is in middle. It’s snug.

2nd thing: yes. It’s connected.

And I have checked all connections several times. I even blew out the connectors thinking it was dust but nothing

hansrensen
If you run MB only with a Ryzen 5600x you will not have video as this processor has no integrated graphics ....

https://www.amd.com/en/product/10471
 
Good Catch 
 
I never even checked, for an iGPU for that CPU..... I just went with, OP knows what they bought
 
enjoy your well earned BR

LDunn5
omg so sorry everyone! but im still baffled -- the GPU does not work at all, and I did try it in a known good mobo. 

it looks like you also tried to test your PC, with a connection to the MB without a GPU - as your first Post mentioned ---> "have taken all but my MOBO out and ran from the MOBO HDMI"
 
As mentioned in post 6 - your CPU does not have the "builtin GPU feature" = "iGPU" --> You must add a GPU to that MB with that CPU for any video. Your MB HDMI can't work, with your current CPU as it does not support video out.
 
If your GPU stopped working & also failed to work in a known good PC, it is most likely a dead GPU. 

Either the GPU was not fully seated & locked into the PCIe slot after changing power cables ..or possibly static discharge?.. just my best guess as to why it died when changing PSU.
 
Not having the GPU fully inserted into the PCIe slot, can allow the contacts to touch in several places at the same time .... look for any burnt marks (from any arching) on the edge of the GPU on the "gold contacts"
 
Do you have access to another old GPU for testing your MB ?

LDunn5
omg so sorry everyone! but im still baffled -- the GPU does not work at all, and I did try it in a known good mobo. 

 
Testing the GPU in a known good PC is usually a good way to see if the hardware has an issue.
 
The GPU might have failed, the timing might have been a coincident. 
 
Do the GPU fan(s) turn?
 
Does the GPU light up?
 
Does the MB give a failed GPU error?
 
As long as you -  were grounded, - installed everything correctly, were not too physical when removing old PSU cables or installing new PSU cables - the change of PSU should not have "killed it"
 
What MB? is it under warranty?
 
What GPU? is it under warranty?
 
What PSU?  new one? old one?
 
Check all connections again
 
test with the case disconnected - All but the start button
 
test with different KB & mouse ...
 
We do not know your experience level ... so sorry if I am mentioning somethings that are very basic ... we All have missed something small before
 
Wondering if OP will ever give us an update?