Newly built computer not working - how do you diagnose?

When I finished building my 4th computer, I turned it on.  Nothing happened, not a single fan rotated nothing at all but silence.  There was one exception the on/off switch located on the motherboard flashed occasionally.  I immediately reviewed all my connections and verified that all cables and wiring were correctly done.  I then tried to turn the computer on again with the same result, nothing happened.
I called a friend of mine who has also built a number of computers and is in charge of his IT department at work.  He suggested that I see if the power supply was working properly.  I brought the computer down to a local computer repair shop and asked them to test to see whether the power supply was working properly. They indicated that the power supply did not seem to be working.  So I called Newegg and asked them to send out a replacement power supply.
I replaced the power supply today being very careful to make sure that all the cables were connected properly.  I turned the computer on and nothing happened except for the on/off switch on the motherboard occasionally flashing.  I find it extremely unlikely that I would have received two bad power supplies so at this point I am at a loss as how to diagnose the problem. Does anyone have suggestions on how someone without the proper tools/knowledge would go about diagnosing this problem?

My first call would have been bad power supply too. But since replacing taht didn't work, I would then next suspect that the motherboard has a major problem or you have something shorted someplace and the motherboard is protecting itself. The blinking light usually means something. Look into the motherboard troubleshooting info and see if whatever light pattern the motherboard is giving off tells you something about the problem.

Also, put the whole thing upside down and shake it to dislodge/eject anything that might have fallen in there like a screw or something causing a short.

Another thing could be that the power supply is not strong enough to power all the hardware connected to it. Especially graphics cards suck a lot of power nowadays (and need special attention with regards to how it is connected to the power supply). Last time I built a PC, I had unproperly connected the video card (there were several option that worked from the cabling point of view - but only one that actually worked, i.e. powered the card properly).

I would check to see if things start to work if you disconnect most of the peripherals (disk drives, video card, etc). Of course it wouldn't really boot, but at least, you could see if the fans start turning.

Just a thought...

Following on the above, if the graphics card needs a lot of power and you did not connect a separate power cable to the card, then it may be trying to draw power from the motherboard. The motherboard then senses too much power drain and shuts down.

Roger

Yes, most better graphics card need a second and in some cases even a third power connection.

I've built a dozen desktops now and I always take a progressive approach. When I start the assembly, I check at each step. If it doesn't work, take everything that isn't absolutely needed away. Remove all the cards, especially the graphics card. Disconnect all the peripherals and hard drives that are hooked up. See if when you power up you get the fans turning and something other than the blinking light. If the fans turn now, hook up one hard drive and see if you get a confirmation beep. If you do, keep going and add the graphics card. And so on.
Since you replaced the power supply, the motherboard is likely the problem. Or as E.J. suggested, something is shorting the motherboard..

It's been a while since the last time I built a computer but - unless things have changed or I have very poor memory - I think you have to plug in and connect the graphic card first before anything else or nothing would happen. You don't need to have the hard-drive installed before you find out if your mother board works. Actually, you don't even need to have the motherboard sitting in the computer case to find out; but you need the graphic card connected.

Thanks for the replies.
Here's some answers to your questions:

No video card at the moment using the builtin MB video Gigabyte Z97X-UD5H:
http://www.newegg.com/Product/Product.a ... 6813128707
No other cards plugged in.

Have shaken the case, transported it too and fro and nothing has fallen out. It is a mid tower case with both sides removed so it is easy to see if anything extraneous has landed on the motherboard. 

The power supply is a Corsair HX750
http://www.newegg.com/Product/Product.a ... 6817139010

I have disconnected the hard drives from the power supply (but left the SATA cables plugged into the MB, do I need to disconnect these also if the power is disconnected?). 

Have checked the continuity of the case power switch and the switch does complete and disconnect the circuit. Have also carefully checked the polarity of the case power switch leads and verified that all the connections are on the appropriate pins.

E.J. good suggestion about checking the MB flashing light but haven't had time to through the pages of the MB manual yet but will do so soon.

Any other ideas as Newegg offers no help other than being very willing to replace parts but they don't offer a troubleshooting service.

The Corsair is more than enough to power a PC with no serious GPU. If you have multiple drives connect only what you need to get going... 1x HDD and 1x DVD and 1 RAM module (unlikely RAM as it should power up). You might not want to but maybe check the CPU and re-seat it? Sounds like a motherboard problem, either a bad connection from CPU or just bad board.

Dick,

Taking away either the power or sata cables will effectively disconnect the hard drives. I always leave the motherboard end connected and disconnect the hard drive end. I looked at the Gigabyte website and downloaded the manual. A quick look didn't reveal any "blink" codes given. There were a number of de-bug codes, but we aren't there yet. Trying to cover all bases, I would try the reset and clear cmos buttons in the upper right corner. Make sure you disconnect the power cord before resetting the cmos. Also, make sure the on-off switch in the same place is on. You said you checked your installation so I will assume the processor and memory are installed properly. If none of that produces results, and since you replaced the power supply, that leaves the motherboard.

In Sept 2013 I built a computer with this Gigabyte MB GA-Z87-UD4H
http://www.newegg.com/Product/Product.a ... 6813128617
Since it has an LGA 1150 socket I tried the new CPU a i7 4790K 4.0 GHz in this older MB - the computer starts and then stops and tries to restart and stops etc.
This would lead me to believe that there might be something wrong with the i7 4790K CPU unless the older MB GA-Z87-UD4H isn't compatable for some reason with this CPU since it was NOT available when this older MB was made even though it is a socket LGA 1150.

Since this processor didn't come out until 8 months after you bought the MB, it's likely that the BIOS needs to be updated to recognize and use the processor which is made on a newer semiconductor technology than the previous. There's more to compatibility than just having the same socket.

E.J. Peiker wrote:Since this processor didn't come out until 8 months after you bought the MB, it's likely that the BIOS needs to be updated to recognize and use the processor which is made on a newer semiconductor technology than the previous.  There's more to compatibility than just having the same socket.

Thanks E.J. thought that it was due to something of that nature.
Is it likely that I screwed something up trying CPU in the old computer?

So would it make sense to try taking the CPU out of the my old MB which I know works and trying it in the new computer or is that a fool's errand since the MB won't power up.
All I'm trying to do is narrow down the items that could be the cause of the problem.

I would try updating the BIOS on the old computer and then putting the CPU back in and going through the BIOS settings to make sure everything is set right. Then you would know if the processor is a questionmark.

E.J. Peiker wrote:I would try updating the BIOS on the old computer and then putting the CPU back in and going through the BIOS settings to make sure everything is set right.  Then you would know if the processor is a question mark.

What in the BIOS settings are likely to need to be attention since there a lot of setting?
I know BIOS basics but nothing too advanced.

Forgot to say THANKS 

The lights dawns just a little late. 
BIOS needs to be checked to make sure the update hasn't changed the original settings. Duh

Just to make sure the right clock frequencies are set and that the memory speed hasn't changed. It should read it but sometimes it takes a second boot-up or a manual intervention to get the speeds right.

E.J. Peiker wrote:Just to make sure the right clock frequencies are set and that the memory speed hasn't changed.  It should read it but sometimes it takes a second boot-up or a manual intervention to get the speeds right.

Thanks again E.J.

Perhaps it would be easier for mere mortals to let Puget Systems build a custom Win 7 machine, or just get an iMac. I'd be very wary of trusting my images to a Home Brew.

Steve Cirone wrote:Perhaps it would be easier for mere mortals to let Puget Systems build a custom Win 7 machine, or just get an iMac.  I'd be very wary of trusting my images to a Home Brew.

Steve it's all a question of $$$. Having Puget build this same computer would cost close to 3 times as much. When you don't have that kind of disposable cash you end up not getting a new computer. A problem like this can hit any computer - it's just the luck of the draw 

Status update. After reading all the dire warnings on the Gigabyte site about updating your BIOS; I decided not to upgrade the BIOS on my old computer as I need to get photos processed before I leave on the 10th. Even though the risk is probably not great I just don't need another problem to deal with before we leave. I think the i7 CPU is probably OK since when I put it in the old computer the system powered up and attempted to boot (unsuccessfully).  So I summarized, in detail, all the steps taken to trouble shoot the problem and sent the summary to Gigabyte and now I await their answer. I'll let you all know what transpires.