I have a friend who has an Optiplex 755 with a bizarre problem. His system is powered on, but there is nothing on the display screen. No apparent mouse or keyboard response. If he presses the power key for 10 seconds, the system seems to power off, but as soon as he releases the button, it appears to power on again, but does not boot up -- just a blank screen. Similarly, if he pulls the power plug from the back of the computer, the system does turn off. But when he plugs the power back in, the system spontaneously powers up, but still no boot and nothing on screen. Once before, he left the system unplugged for two days, and when he finally plugged it back in, it did boot up. (I didn't believe him at first, but I have just come from his house and saw this for myself.)
Does anyone have any ideas what could be causing this behavior and what to do to get his system to act normally? Does this sound like a stuck power switch? Any and all suggestions or comments would be appreciated. Let me know if there is any additional information that might help in diagnosing this problem. Thanks in advance.
Doubt it's a stuck power switch? Cause when it does power on it should recognize a OS, it's not even getting there. Possibly a hard drive gone bad? Are you able to get into the BIOS or boot from the OS CD disk? The hard drive should have a smooth spinning sound when running. See if the hard drive is making unusual sounds, here's a link that may be of some help.
Also is the power supply fan running when the computer is powered up? Possible bad power supply, but when they go, alot of the time the computer is completely dead. Or if the power supply feels hot to the touch that is a bad indication.
You can try and pull all the ram out and then power up the computer and shut it down. Then add one ram module back at a time as you power the computer on and off till you have them all back in place.
What color is the power button when it won't boot? And is it solid or blinking? See page 65, here for the details.
Are any of the 4 diagnostic LEDs on when it won't boot? Error codes are on page 67 at that link.
When was last time motherboard battery was replaced?
Forum Member since 2004
I am not a Dell employee
Bad power supply, bad ram, bad hard drive. The diagnostic lights on the front should say something no lights means bad power supply.
I would go along with the "bad power supply" theory. A stuck switch would be quite rare, I imagine it would have to be shorted out to cause that problem. Those switches are probably rated for a gazillion cycles.