Computer question

Check your ram sticks. Sometimes ram can cause a "no signal" even though the computer turns on. Move the ram to different slots if its a 4 slot motherboard. Also, does your CPU have an integrated graphics output? You could also check to see if its not a graphics card issue. If your CPU has an IGPU, you can check that by plugging in your display to the motherboard IGPU and see if you get a picture. CMOS batteries are easy and cheap to replace, can just go to a store and buy those.