My pc does not always start

I found 3 mini pc’s one of them always starts up and the other 2 didn’t start i cleaned all of them up and after cleaning the other 2 both started but now they won’t start anymore could anyone help me

If the PCs use external power bricks it’s highly likely they supplies are done. You don’t say what kind of PCs they are, shuttle etc so I’ll assume when you say mini you mean small form factor? From your descriptions though it defo sounds like the PSUs are done. Try the working one from the pc you said works fine (if it’s the same)

Thanks ik look for a other of thats the problem