Problem - Monitor will not turn on from cold boot/wake

Although my system appears to boot normally, my monitor will not turn on from cold.

History:
The system has never worked correctly. I built my father a new mid-range gaming PC for his simulators about 4 weeks ago. I have reasonable experience building PCs. I've never had any problems with systems I've built in the past. I own and use a static band when tinkering.

The Full Story:

• If I reboot the system - no problem.
• If I power down or let the system sleep then restart or wake it immediately or within a few hours - no problem.
• If I power down or let the system sleep then restart or wake it after several hours - the monitor will not turn on.

This is not an intermittent problem. I can reproduce with certainty every time. I cannot work out exactly how long the system has to be off before the monitor won't turn on - at best it is between 4 and 7 hours before the problem occurs.

I do not believe there is a problem with the system boot sequence. There are no error beeps. The CPU, PSU, fans ,HDs, lights all make the right noises/flashes when the system boots even when the monitor does not turn on.

To get the monitor working - I have been waiting till the system has finished its boot sequence then doing a hard reset (holding down power button - using reset button does not work). Most times I only have to do this once however periodically I have to do 3 or 4 hard resets before the monitor turns on - VERY ANNOYING!

The Specs:
All hardware is new out of the box.
CPU: i5 3470 @ 3200Mhz
MB: Gigabyte Z77-D3H
RAM: G-Skill 2x4Gb DDR3-SDRAM 800Mhz
CPU cooler: stock Intel
Video Card: AMD Radeon HD 7800
Monitor: LG Flatron E2351
PSU: Seasonic 620W
HD: OCZ Vertex SATAII 120Gb SSD, Seagate Barracuda 1Tb HDD, DVD writer.
OS: 64b Win7 Home Premium
No other hardware.

I have tried the following without success:

1. Updating the latest GPU drivers & windows updates.
2. Different DVI/VGA/HDMI connectors to the monitor.
3. Alternating the DVI ports on the GPU/MB
4. Taking whole system apart and re-seating all components and reconnecting all PSU plugs. following the steps in this link carefully!.
5. Tried different monitor on problem PC.
6. Tried disabling PLL Overvoltage in BIOS - as per a number of other suggestions around PC's not waking from sleep.
7. Switching monitor off and on (repeatedly) after boot has no effect. Get monitor no input message and monitor goes back to standby.

Any help would be appreciated. I can just imagine my discussion with the shop if I have to take components back and I turn it on in store and everything works wonderfully!!

Thanks,

 

It can only be three or four things, First Video card is bad, or Motherboard or Power supply, and last would be a bad monitor.. Try the monitor on a different system..
You will have to narrow it down..

 

OK. Finally solved it!!! I tried a different PSU and had the exact same problem.

As I was gazing into the depths of the case wondering where too now... it occurred to me that there are TWO GPU slots. I swapped the GPU to the other slot and voila it works perfectly!