I had some display problems with an old system, only showing signal once every five boots or so. Immediately, I assumed the 6600GT had finally given up, as the monitor worked fine when plugged into my netbook. I needed to replace it anyway, so instead of putting a new card in a slow system, I thought I'd go out and get a Motherboard, CPU and RAM. Still have problems.
MB: Asus P8P67-LE-V3
CPU: Intel i5-2500K
RAM: 8GB Kit 1600 G.Skill Ripjaws-X (2x4GB)
GPU: 1GB ATI Radeon 6850 (HIS)
(PSU: 700W Thermaltake LitePower)
Old parts (known working):
HDD: 1TB Hitachi SATA (3GB/s, 7200RPM)
HDD: 200GB Hitachi SATA (3GB/s 7200RPM)
Optical Drive: LG DVD-RW
(PSU: 430W Thermaltake)
PROBLEM ONE [SOLVED]: Okay, so I put it all together, using my original 430W Thermaltake PSU, thinking this would be sufficient. I booted it up and it went through POST first time, everything connected (I thought I'd try my luck), but no signal. I jiggled the monitor cable (VGA via DVI-I adapter), to no avail. I thought of two possibilities, either a dead GPU or not enough power form the PSU (GPU manual recommends 500W minimum). Ironically, the system worked with the old 6600GT, but I had parted with good money and needed the extra GPU power, so wasn't going to give up on the 6850. I tested the GPU on a friend's machine and it worked perfectly, so went out and bought a 700W PSU. Happy as Larry, I installed the new PSU and booted up. Success, for a little while. Still, the monitor would switch to standby. I figured my notebook and 6600GT tests were pure chance and sure enough, wiggling the VGA cable seemed to work (I have reduced the cause to the monitor itself, since).
PROBLEM TWO [MYSTERY]: I loaded up a Ubuntu Live CD (11.10), knowing it had worked with the 6600GT in my early new system tests. Alas, it would not boot past the initial splash screen, instead showing a flashing underscore (not able to input commands, keyboard inactive). I read this happens when the disc has lost integrity. Checked another disc prior to loading, but still no boot. I disconnected the optical drive (which had always been sketchy) and decided to boot off a USB HDD. I changed the boot order to the connected device and restarted. Since, it will not POST. No display, no beeps.
WHAT I HAVE TESTED:
I reset the CMOS and RAM jumper and unplugged the USB, reversing my steps. Still, no POST. I then breadboarded, installing one component at a time. I got the absence of RAM beep sequence, but after installing each stick in all possible combinations and DIMM positions, it did not beep for HDD or GPU. Installing everything again, still no luck and no POST. I switched GPU for the 6600GT and also tried each HDD at a time. The CPU fan, 8-pin, 24-pin connectors are all seated correctly, as is the RAM (which I have removed and replaced many times).
Do you have any idea as to why this may be occurring? Is it worth testing the PSU for the old 430W and 6600GT (shown to work previously)? Could it be the Motherboard or CPU?
I have built many systems and they usually boot first time, every time, aside from a couple of RAM failures.
Alright, time for an update. Should anyone else go through this, I will describe the tests I performed.
Step one: acquired second machine, loaned from a family member. I'll refer to my machine as 'one' and his as 'two'.
Step two: removed power supply from one and placed into two showing no fault. Swapped GPU from one to two to ensure adequate power supply; no fault.
Step three: breadboarded one on anti-static, non-conductive surface, adding each component one-by-one to detect potential problems through POST beeps. Beeped for no ram, but after inserting each stick individually, did not detect absence of HDD or GPU.
Step four: take one to parts shop, have them breadboard test with new motherboard of same model; perfect POST.
There you have it: simply tests and simple diagnosis. The parts dealer said he gets returns of about one in twenty motherboards, regardless of manufacturer, while PSUs are returned significantly more frequently, depending on manufacturer.
Despite the time it took, definitely worth it. To get the parts shop to test in the first instance would have been difficult at best and blindly replacing the parts most likely at fault (like a PSU, for example), could leave you with not enough time to return other parts if they are the actual culprits, having to deal with manufacturer warranties and lose out on postage (in Australia, retailers are within their rights not to accept a return seven days after purchase).