Question Why my hp will not show video or keyboard

[Kjhabit]

My used yard sale hp prodesk 600 g4 will not put video out, will not light up keyboard or take keyboard commands and all USB ports seem to attempt contact with thumb drives but will not finish post?!? That’s a lot to say. Striped it down to psu and cpu: get memory post code. Replace memory and disconnect cpu: get post code for cpu. I. Do not have original hdd and I am in fear that bios may have a security lock?! But why would it not display video?? Thanks!!

 

[rgd1101]

was it working after you got it from the yard sale or are you trying to fix it.

 

[Kjhabit]

He said it worked fine and he kept hdd for privacy. I actually have two of them but the other is for parts.