|The power button on a tower/case rarely breaks & is rarely a problem. It's just a momentary switch like a doorbell button. A toggle type switch should NOT be used, in fact, it will damage your system. What type of switch did you replace it with?|
"the monitor says signal not found"
That means just what it sounds like - the monitor isn't receiving a signal. The monitor is most likely OK, the problem is with the tower. For whatever reason, it's not sending a video signal to the monitor. Could be a bad video card, bad motherboard, bad/weak power supply, etc. It's impossible to say based on the info you provided.
"wait for the charge to leave the CPU"
Please don't call your tower a CPU. It urks a lot of people, including me. A CPU is a chip that fits in a socket on the motherboard.
What is the make/model/wattage & amperage specs of the new "power box"?