monitor cuts off after 50 min

[rpjones]

i have a monitor that is cuts off after 50 min. if you turn of the monitor for a couple of minutes it will come back on and work for 50 min. i have changed the monitor, all cables to pc including usb and printer cables, speakers vga cable the entire pc. pretty much everything but the two printers that are hooked to the pc has been replaced, and i mean everything has been replaced. i have tried put a ups on the monitor and pc to combat power slopes but the problem is still happening can anyone help me?

 

[bobbknight]

energy star?
bad monitor power supply.

 

[rpjones]

have changed monitors cant be that