No beeps, no display, but fans spin

[Danknank]

so I recently build a new computer with only the GPU is used in my new build, which works fine with no problems. but then I tried to put together my old build which runs an fx 6300 and a gigabyte ga-78mt-usb3 it won't boot. I have a motherboard speaker and it didn't beep. so I tried to search the internet for answers, one answer is to find a new power supply which I bought yesterday (seasonic 430w eco 80+). but it still won't turn on. someone suggested to swap the CMOS battery which I did also but still with no leads. all the fans spins with no exceptions including the HDD and the GPU fan, the display is also blank.

someone please tell me what part that could potentially have been broken

 

[Barty1884]

What are the full specs of the system that won't boot?

 

[polis_putrus]

Its the ram, make sure there is no dust on the ram or in the ram slot, after cleaning dust, if there was any, and it still doesnt work, the gently wiggle the ram, turn it on, if no display TURN OFF then wiggle ram again keep trying, it always works for me, Im 100% sure because Ive done this with about 5 computers throughout my life all had black screen I did what I explained above and it worked, let me know if it works, do not worry it will not cause any damage, Thank You.

 

[Danknank]

What are the full specs of the system that won't boot?

fx 6300 3.5 GHz
^the motherboard that I wrote before
8gb 4x2 ddr3 v-gen
r7 240 ddr3 2gb
500 wdc blue
seasonic eco 430w
gammaxx 400

 

[Barty1884]

Take a look through this checklist.....

It's usually something pretty obvious.

Personally, I'd start with reseating everything though.

 

[Danknank]

Take a look through this checklist.....

It's usually something pretty obvious.

Personally, I'd start with reseating everything though.

ok i already found an answer, for some reason before i swap my casing to something smaller it wont turn on no matter what i did to it. but after swapping the case it magically turns on (?)
thanks for answering though