PC hardware issue.

I've been building PCs for nearly 30 years but this issue has got me puzzled. So there I was transcoding a video and PC just went off. No flash, no bang, just off. Right first thought PSU has died. Got an old PSU and tried that - no joy. Took both PSUs and did the insert paper clip into mains plug to test if they are actually working - both PSUs came on with this test. So has to be motherboard. Bought a new motherboard, inserted CPU, RAM and connected cables, turned on got message "No display". Swapped out graphic card for an old one that doesn't need any power straight from PSU - still no display. Swapped out PSUs - same message. Right has to be CPU. Bought new CPU, installed it on new board, turned on, power light came on, heard CPU fan speeding up and down but still no display. Cleared CMOS tried again - same result, swapped out RAM from another machine, swapped PSUs (again) - same result. Machine sounds like it is trying to start but no display. Moved entire machine to a different power outlet in house - no joy. Tomorrow, out of desperation, a new PSU will arrive. If this don't work I am lost. The whole system will be new. I don't connect HDDs/SSDs when powering on as all I want to see is the POST screen.
What is going on?

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Did you try it without the case?

I've lost count of case mounting issues. Yes there can be more like that motherboard with a bad manual that had folk putting a HDD LED on the RESET connection. You don't need anything other than the power connections and the power on to test. Here's a video about this.

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Useful hints.

I am going to have to assemble it outside the case I guess, something I hate doing. Regarding the front panel connecters - it seems that the colour coding changes every so often. In the manual the colour codes referred to are purple and white for positive and negative. Not one of my front panel connecter's wires is either purple or white. They are two-coloured which is hard to define. I have ordered a power switch that I can easily attach, in the future (which is purple and white), to the motherboard as to avoid mounting it in the case. This won't arrive for some days so tomorrow will be a day where the components are spread out over the floor. Man I hate this part.

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Of all the front panel connections I only need on.

The power on button. All the others are optional until it's turning on.

I wasn't clear about another thing. If the CMOS CLEAR JUMPER IS ON, it may power up but do nothing.

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Another thing...

Waiting for a new PSU to arrive today and a thought from the past hit me. I am using an AMD FX CPU and maybe the board's BIOS isn't recent enough to access the CPU. This happened to me about 4 years ago. I had to install an older CPU a Phenom, update the BIOS then install the FX CPU. This could be it - if it is I have several pieces of hardware to return with lame excuses.

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Just connected a brand new PSU and still no display, just the CPU fan whirring up and down. It is now effectively a brand new system. Has to be the motherboard's BIOS not recognised the CPU.

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Update #2

Tried system with a FX-6300 and a FX-6100, they have different architectures - still the same result. Ordered another motherboard, different manufacturer, Asus this time instead of Gigabyte.
This is costing me a fortune.

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Nothing left to test.

Tried 2 different motherboards from different manufacturers, cleared CMOS on both, 3 different graphic cards - 1 from the system I am using now so it works, 2 sets of different RAM modules - different capacity, different speed, different manufacturer, 1 set from the system I am using now so they work, 3 different PSUs from different manufacturers, 2 different monitors inc. their DVI and mains power cables - both monitors work fine on the system I am using now. This brings it down to it HAS to be the CPUs. The existing one that was installed was an AMD FX-6100, the new one I bought is an AMD FX-6300. No display on every configuration I have tried with above parts. The system appears to run fine - fans spin and LED on motherboard lights up when it has power. Finally, YES, I have connected the 4 pin or 8 pin (depends on the motherboard) CPU power.
If anybody has any other suggestions... well I would be amazed if there are any.

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But, But, But,

What about doing as Bob asked ?
What about a bench test ?

Did you test any of these parts on a piece of cardboard outside of the case?
You can swap parts till your blue in the face and still never go through the process of elimination.
What's up with that?

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All the components are outside the case. The case is near enough so that the front panel power switch reaches.

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You have replaced everything but...

the cable. And on the bright you have enough to build another computer so no money wasted.

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Tried cables.

As I said I connected the monitor and its cables to another PC and they work fine. Seems I may have to go Intel after never using their CPUs... ever!

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Maybe a dumb question but , Do you have the CPU inserted properly, no bent pins ?

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You mean "hairs"? These new processors, it's almost a joke to call them "pins" anymore. I've had to use a toothpick to comb a few of those back up, they are too easy to bend. The last AMD processor that had decent "pins" was the 754.

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Splittin' Hairs ?

Well, it sounds like it's easy to bend them . At any rate I thought I'd toss the question out there..

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mechanical pencils

with the lead removed is a good one to slip over any of the newer "pins" and lift back into almost perfect position. With about 30 pins on a side for a 1.5 inch CPU, I have to use my reading glasses and a magnifying glass to check for any bent ones.

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That's a great idea.

I hope I can remember that when the time come.

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Not a dumb question.

At this point there aren't any dumb ideas. The pins are all good on both CPUs. The CPUs slip into the socket snuggly and can only be inserted in one orientation.

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onboard graphics

What's the graphics on these motherboards? Using a PCI card or the onboard video? Maybe the FX chips interfering with the video feed?

I read through it all again. Notice FX chips have varying voltage settings allowed for RAM.

Are the PSU you have up to running these "hot" chips, enough amps to provide the power? Although the entire PSU should cutoff if that's a problem.

You've never said what motherboard model it is. It might only do 4 core or less processors.

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The first board I tried was a Gigabyte 970A-UD3P. The board I have now is an Asus M5A97 LE R2.0. None of these boards have on board graphics. I haven't ever seen an AMD socket motherboard that has on board graphics whereas most Intel boards do.

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Oh but you will...
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(NT) All mine due with the 785 chip
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Build another PC...

... that doesn't work!

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I keep Sempron 145 on hand

several new in box to use for testing AM3 and AM3+ motherboards. Cost from EBay is $25 or less and no big deal if one burns.

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Funny you should say that...

I've just bought an AMD Phenom II x 2 955, socket AM3 to test things. I remember I had to do this when the FX series of CPUs were released in order to update BIOS then swap out the Phenom for the FX.

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What's next ? Confused

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... for the Phenom II x 2 to arrive. Cost £17.99. Also may have a Phenom II x 4 on the way, depends on Ebay auction.

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The suspense is killing me

LOL Silly

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OP got a real puzzler here.

I am scratching my head really hard...nothing but dandruff comes out.

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Nothing more apparent...

... that you have dandruff than when you scratch your head over an empty black PC case which is what I've been doing for a week.

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And when it eventually works...

... just to throw this out there while I wait for CPU to arrive. If, this I am not sure about yet... if I choose to reinstall Windows, currently using 10, then don't I effectively have a new system? Can I go straight to installing Windows 10 and not install 7 first? Would Win 10 be recognised as being licensed to me?

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