Optiplex 755 only turns on through power supply button, no video output.

I have gone thru these steps on optiplex 755 and always the same sounds.  6 buzzes: 

1: 3 second buzz followed by same length pause, then

2: 3 second buzz, then immediately,

3. another 3 second buzz, then immediately,

4. another 3 second buzz, then a normal 2-3 second pause

5. another 3 second buzz, and quickly after

6. another 3 second buzz.

That sound familiar?

Any help appreciated! 

ive got the same problem with HeadOnAPike, my system is optiplex 780 i have to follow your instruction until point 8 and i dont hear any beep from the motherboard, the led on the motherboard turn on and i just hear one beep. what should i do?

That power supply sounds like its failed!  There are the 4 diagnostic lights on the front of Optiplexes - but they generally dont light when a power supply fails - do they run through sequence - i.e. they flash various combinations as the PC starts? If no lighting up then its not getting to even run the diagnostics which is usually power supply failed - but they are easy and cheap to replace.

If they do light up then whats the sequence they stop on?

The button on the power supply is a quick test button - i.e. when the PC is off press it and it should show a green light. Its only a general indicator though.

i have try to replacing the new power supply, but nothing happen.. I guess the problem is between the motherboard and the io panel, but im not sure..

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Hi, i have a problem with my system unit " DELL OPTIPLEX 755" No Power...plzz..help..,,

Symtoms Are:

• No response from the power button (stays off)
• Power light responds with blinking amber (orange) light

when I turn my OptiPlex 755 on it will not detect any bboot device

when I tray to tan on my dell optiplex 755 min tower it will not show any thing on the monitor and on leds  will light up and when hold the power baton it will not shut down will just restart.

sir my computer dell optiplex 755 tower working good but power buten not work .

cmos out than computer start plz help me .

I happened to me something like, finally had to use the warranty.