Optiplex 780 desktop not powering

Good day!

To get a better understanding, can you help me with the following information:

• Were there any software / hardware changed made on the system recently .
• What is the colour/status  of the power button ,do you see any of the indicator lights or hear any beeps from the system.
• Do confirm the troubleshooting steps performed before you replaced the power supply unit and battery .
• Have you tried performing the power cycle test on this system by disconnecting the system from wall socket , press and hold  the power button for 15-20 secs then connect it back to wall socket and try to turn on the system .

Also do reply to this post with the service tag of the system via private message so that I can look into the specifications of the system .

Awaiting your reply .

Kind Regards,

No new hardware or software. 

There is no color status of the power button, doesn't get that far. As I said, it's the pre-cycle when the computer is plugged in that is looping. I live where there is not 24/7 electricity so I see this cycle on all the dells when the power comes on.

There really isn't a lot of troubleshooting that I can do at this point, this is prior to being able to power up the system. I either can or I cannot. It is as though there is a static charge blocking the pre-start test. This is before the BIOS test. I'm assuming the test is part of the "what should the computer do when power is restored" setting.

Yes, I've drained the power many times, with the CMOS BAT in, without the CMOS BAT.  I've even tried putting a hammer next to it as an unspoken threat. The only consistent is unplugged, CMOS BAT removed and wait two or three days, then I get 1 to 4 starts before back to square one.

Hi,

Thank you for the reply!

Here in this case just wanted to confirm when you mentioned you  have replaced the power supply unit ,do you mean that the same issue is seen with a different power supply unit and different power cord.And on the power supply unit we have a tiny black button with a small bulb next to it ,if the black button is pressed does the light come on.

Also do forward the invoice copy with which the system was purchased ,system owners name,physical address ,contact no ,email address  via private message so that I can check the details of the system .

Awaiting your reply .

Kindest Regards,

I have tried a power supply from a working 780. Yes, the light comes on and the fan turns at slow speed when button pushed and I have tried a larger, 500W brand new out of the box power supply. there is no change at all.