Question CPU fan full speed but no boot

Mar 19, 2020
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Hey guys, I have a computer that will not boot up.
it is an Acer AX3475
Has
AMD A8 5500
Just changed the AMD Radeon HD 7350 1024 MB to a nvidia geforce gt710 cause I thought it had failed
Has 8GB DDR3 memor

The CPU fan goes to full speed but there is no beeps from the mother board, there is power at the Ethernet light, no other lights are coming on. I change the graphics card out cause I thought it had failed but that wasn’t the case. I had an old computer with a new power supply so I pulled it out and plugged it in and that didn’t change anything either. I have unplugged the ram chips and plugged them in individually and no change.
i am thinking that it is either the cpu or the mother board that has failed but I don’t know enough on how to test either component or what to replace them with.
i know enough about computers to be dangerous but that’s about as far as that goes