UKC

Ive built my own pcs for years and generally know how to troubleshoot them. My parents pc stopped working in that it would not power on so I checked the usual stuff

Stripped out all the non essential components and used the onboard graphics port, all RAM out except one nearest the CPU. Now its just a bare board except for RAM, CPU, the two power connectors and the power button. Fans run ok but monitor still saying no input signal.

Went through the other 3 sticks of RAM but no change. Removed the CMOS battery, waited 5mins then replaced. Nothing.

Tried different monitor, nope.

Thought maybe CPU was kaput so ordered a replacement (2nd hand as its an older processor, assured it is tested and working) Nothing.

OK maybe MoBoard, ordered a replacement, still nothing.

Tried a combination of both CPUs and Boards, nothing.

Tried a different PSU I had spare, nothing.

Only thing Ive not been able to try yet is a different stick of RAM, but surely all 4 wouldnt be dead at the same time would they?

Anybody got any other thoughts on this oddity?

Too confusing.

But you obviously need to be working from known-good positions. How do know, for example, that the new mainboard you've got is not DOA?

Double-check all the psu cables are hooked-up to the motherboard. Particularly the cpu supply.

I assume you've tried different monitor cables?

And you didn't mention the hdd/ssd. Tried swapping that with a known good?

If it has a cd/dvd drive, try disconnecting the hard drive and see if it will boot from a bootable cd. Or a usb stick.

Assuming this is a desktop, possibly an issue with the power-on pushbutton on the front of the case?  Alao sme older desktop pcs have a power rocker switch on the back panel that isolates the motherboard.

Other than that, the only thing that occurs to me is a corrupted bios. There may be a jumper that lets you factory reset it.

A really bad power spike could have fried all four, but it seems unlikely.

A couple of odd ones that I've seen.

Some motherboards have a jumper to enable onboard graphics. I once spent ages looking at a blank monitor before I found that.

I once had a PSU die and it took out the MB, CPU and RAM with it.

I didn't mention disc drives as it's irrelevant, not even getting to bios

I don't think this does but will look closer

Edit: no it doesn't

Any diag/power LEDs on board? Have you tried to reset the BIOS? I've had corrupted BIOS or UEFI giving boot problems before. A deep power cycle and BIOS/UEFI hard reset (shorting the pin) helped.

Of course, it wouldn't help if any HW components are caput, but just having a scrambled BIOS or UEFI might exhibit pretty much same symptoms to actually faulty HW, even if it's just a SW problem.

Ordered some RAM, can't think of anything else

If it were bios, the one on the replacement board should have sorted that issue. No LEDs and no post beeps either

Sorry, I missed that you replaced the board as well...

At this point, I'd go with single channel memory, one stick at a time. You have probably ruled out PSU problems by exchanging it. After that, it's likely just the magic smoke escaping unnoticed...

I had a possibily similar problem with a PC a few years ago.

I'd press the On button and got nothing. After checking a lot of things I found it was the On button. Something had gone wrong with it and pressing it did not power up the PC.

Fortunately I had a spare case and when I put all the bits in the new case everything was alright.

Dave

What exactly do you mean by that?

Will not turn on power supply?

Will not boot to BIOS?

Will not boot to OS?

If it powers up, but BIOS finds missing HDD or memory, it will usually beep or flash LED with some diagnostic code.

If you're not getting beeps or flashes (or any life from fans), then it sounds like PSU is not coming up; could be the PSU brick, could be onboard supplies, or could simply be the PSU_ON line, from the switch, or on the motherboard.

So you've already tried multiple:

1. CPU
2. Motherboard
3. Ram
4. Graphics card
5. Monitor
6. PSU

Surely the only thing left is the case and the cables. But if the fans power up then I don't think it's the ON switch that others have suggested.

Or you've got two dead CPUs/motherboards/etc, but that seems unlikely.

Also, dead RAM should give a POST beep. So I don't think it's that.

So the fans start, and you've replaced everything but the monitor cable........

Sounds like you have parts there to build a second functioning machine. Does that one work?

Does the num lock light respond to the num lock key?

Edit: hang on. This is going to be a really stupid question, like to the point I'm going to apologise in advance for asking it, but... You have checked the monitor(s) is set to the correct input, right?

Ha yes checked that and have tried both dvi and dsub cables

It doesn't seem irrelevant, as its one of the parts (along with the case) that you haven't swapped-out. If the drive controller (or sata/ide cable) is faulty then the bios may be stuck on trying to initialise the drive.

Have you tried booting into the bios's interactive mode using F2 or whatever?

 I presume he's already tried to boot it with all SATA/IDE cables unplugged from the motherboard. If not, that's the next thing to try.

The BIOS would normally complain loudly about that, surely?

It's not the days of MFM drives anymore. And bad RAM or VRAM doesn't always make the BIOS beep like it did, since it's UEFI now. Even back then, the beeps weren't always conclusive.

Which brings the question, what's the OP's video output? PCI Express GPU? iGPU from the MB or CPU?

Have you tried a different GPU?

If a PCI Express GPU, maybe that's OP's problem? I've had GPUs stuck in a wrong power mode or whatever after a botched up in-standard UEFI/BIOS/PCI config or glitch. Sounds pretty similar – the board came up, CPU came up, but no BIOS or UEFI or output. Maybe your Video BIOS got corrupted?

Of course, there is the time tested BOFH option to get it up and running – have you tried sacrificing a black goat or at least a cockerel? That usually works wonders

The on button header posts on m/b can be "pressed" by bridging them with a small screwdriver, that checks if the switch works (if you don't have a continuity/multimeter to test the switch directly)

In your OP you say you removed most of the components and used the mb graphics port. Did the pc originally use a discreet GPU? If so what is the CPU? Recent CPUs tend to have the onboard graphics in the CPU not the MB. The CPU family often includes some models with inbuilt graphics and some without. The motherboards will all have a graphics out port in case the installed CPU has inbuilt graphics. An MB with a graphics port and CPUs without inbuilt graphics would result in what you are seeing.

Should do. But in my experience, BIOSs on older machines can be of dubious quality when it comes to handling odd errors.

I haven’t understood most of this thread but now I’m hooked and looking forward to the final episode that reveals the culprit…

Good luck!

It's the fuse in the plug.

Given the number of things that have been changed - this is somewhat reminiscent of 'Trigger's broom'!

I'm probably 15 years out of date when it comes to building computers, but as I understand modern motherboards typically don't have the little black speaker beeper thing and I think (don't quote me) you need an external speaker to hear the beeps. Troubleshooting without beeps in  POST is going to be hard as it's just trial and error.

I'm still not clear what happens when you switch it on, is it acting as though it's just unplugged, or do things like the fans spring into life? If fans turn on, definitely hook some speakers up.

Other things that come to mind, there used to be a couple of pins you can jump to switch it on, should avoid anything case related causing issues.

There used to be a way to jump pins on the PSU to force it to switch on, could be worth trying that.

Otherwise, in your position I would start with a known somewhat compatible working rig, and swap parts one at a time to see where it falls over.

It's got to be something dumb like a dodgy cable, as everything has been changed. Do PSU's still connect direct to the motherboard. I trust there isn't a separate wiring harness or anything like that which could be the issue?

I think I had a bad USB keyboard preventing boot once, but I think I was getting some POST beeps. I assume you’ve tried swapping out keyboard and mouse? 
Of course this is the problem with other people’s PCs that ‘stop working’: you’ll find the problem eventually and then someone will say ‘oh, I did spill a cup of soup on the keyboard’. 

You said you took the CMOS battery out, left it for 5 mins, and then replaced it.

Did you replace it with the same battery, or did you replace it with a new one?

I recently had some odd problems with a machine at work which was caused by a dead CMOS battery. Some of it was similar to what you describe - for example the fan was running ok but the graphics card wasn't behaving and I couldn't boot to UEFI. A new battery cleared it all right up!

yes new battery

I may have missed it, reading thorough the thread. Have you used a different monitor? Could be a fault on the monitor input.

Apologies if you've tried this, or its a bit egg sucking.

fans running? 
num lock light?

I'm not sure the num lock light is a reliable indicator of anything here. When you press the num lock key then the keyboard sends the key's scan code to the pc. Software on the pc is responsible for tracking whether the num lock is on or off, and responds by telling the keyboard to turn the light on or off. All the keyboard does is remember the current state of the light.

If an OS is running then the keyboard driver is responsible for making sure the light behaves as expected. If only the BIOS is running then it depends whether the BIOS vendor decided to support num/caps/scroll lock in their keyboard handling. Older machines with limited BIOS flash memory may only support caps lock, or maybe not even that if they don't use any alphabetic text input.

Do we know how old this machine is? BIOS or UEFI?

Bios as noted previously.

Not got keyboard or mouse connected, just as noted previously cpu, mobo, one stick of ram, power cables, just to see if it will boot to bios screen. I appreciate there has been a lot of replies but all there in my original message

Doesn't POST look for a keyboard as part of the BIOS bootstrap sequence?

If you don't have a keyboard attached, the boot sequence may be failing at the hardware polling stage.

Edit to add link:

https://www.technewstoday.com/power-on-self-test/

Yes, so if it lights up that tells you a lot.

If no keyboard attached, you'd expect that old classic "Keyboard not found. Press F1 to continue"

I certainly suspect the keyboard.

I would spend a tenner on a POST card to determine where the POST sequence was failing.

https://www.amazon.co.uk/Computer-Motherboard-Diagnostic-Ming-sound-Workman...

I appreciate its probably all there in your original message, but people are replying in an attempt to be helpful.

Ok. But I asked because some people use BIOS as a shorthand for any boot firmware, including UEFI.

Suggestions:

- Try a known good hdd+cable, case, and psu. I cant see any indication that these have been swapped-out. Without eliminating them then its hard to suggest much else.

- Is the RAM stick still one of the originals, or the replacement that you bought?

- Post exact model of PC, cpu and motherboard

- Connect a keyboard via ps2 socket if there is one

My point was that if it doesn't light up then it doesn't tell you a lot.

I've now exhausted all suggestions and options and nothing works. 

For those suggesting HDD, mouse, keyboard etc it's not needed for a pc to load to bios so I left them off to make things simpler.

Tried replacement CPU and mobo (obviously not 100% sure on these but eBay sellers both had positive feedback). Tried combinations of both CPUs and both motherboards 

Tried new stick of ram in all slots

Replaced CMOS battery 

Tried different PSU

Tried onboard graphics port and working graphics card from another machine

Tried different monitors and cables.

I have closely inspected both boards and CPUs and all looks normal, all jumpers are where they should be and power switch works fine.

The CPU is definitely getting power as it feels warm after being on.

I don't like giving up but having spent many hours on this now it's just not worth any more time.

For those interested it's an Asrock NF6G-VSTA board and Amd Athlon 64 X2 ADX640 processor in my parents PC

You (most likely) will need a keyboard plugged in.  Then while you're at it try the NumLock key just for fun.

Is it in a case or on the bench? Only time I've had symptoms even close to this were when there was a misplaced and almost invisible standoff shorting something out. The system worked fine in the open air but it would spin up the fans but shut itself down immediately when built up in the case. That was a frustrating few hours.

That's an impressive amount of effort and expense to go to try and save a 20 year old PC. It's an AM2 socket and DDR2. Is it worth saving?

I would just go on eBay. Search for "Dell Precision T1650 Tower PC Intel Core I7-3770 @3.40GHz 16GB RAM 128GB SSD" and get a fully working PC for £50. Still 10 years old, but significantly more modern.

They can't give up now, we all need to know what it was! 

You have changed as much as a ship of Theseus. Likely it's just broken, return it and get a new one, if possible.

Not much to note about Amd Athlon 64 X2 ADX640 processor, except that it does NOT have integrated graphics, so no graphics card no picture!

Try putting a graphics card in and plugging your monitor into the graphics card *not* the motherboard/onboard (that you don't have!)

Ref: https://www.techpowerup.com/cpu-specs/athlon-ii-x4-640.c787

The motherboard has integrated graphics and a vga connector

https://www.asrock.com/mb/nvidia/alivenf6g-vsta/

Years ago (late 90s) my mother did something similar to you, opening case and having a good prod.  I was visiting and told her to put it back as it was, before I arrived.  Turned out the VGA cable wasn’t correctly seated. That was the only problem. 

I am afraid you are now in the position that you’re never going to work out what the original problem was as everything apart from the plug fuse has been changed. 
 

As others have said it does seem like an awful amount of effort. What is so valuable on the hard disk that warrants it?

I was perusing thr mobo manual* earlier and I have a kind of theory.

On p.16 it describes how to use two monitors, one with the the on-board graphics and one with a graphics card. Pretty cool for 2007 I guess. It says:

Boot your system. Press to enter BIOS setup. Enter “Share Memory” option to adjust the memory capability to [16MB], [32MB], [64MB], [128MB], or
[256MB] to enable the function of onboard VGA/D-sub. Please make sure that the value you select is less than the total capability of the system memory. If you do not adjust the BIOS setup, the default value of “Share Memory”, [Auto],
will disable onboard VGA/D-Sub function when the add-on VGA card is inserted to this motherboard.

(my emphasis)

So the bios can disable the on-board graphics if a graphics card is beng used. I'd expect it to re-enable it if there's no graphics card, but maybe it doesn't. And maybe both motherboards have been used with graphics cards over their lifetime, and this is reflected in their bios settings.

So this might possibly explain what you're seeing (or not seeing) with both systems.

So it might be worth re-initialising the bios's cmos ram and seeing if this makes a difference at boot. This is described on p.18 and involves shorting jumper pins 2 and 3.

I get that you've abandoned this. But I though I'd mention the above as something easy to try.

* https://download.asrock.com/Manual/ALiveNF6G-VSTA.pdf

There is so little to go wrong, I'm intrigued...

• If the CPU has been swapped, then it's unlikely to be the CPU
• If the motherboard has been swapped it's unlikely to be the M/B
• If graphics is in M/B then that's already been swapped, so unlikely to be graphics "card"
• If the RAM has been swapped it's unlikely to be RAM
• If the PSU has been swapped it's unlikely to be PSU 

The only remaining parts to swap for investigation are monitor and VGA cable and power switch. (Did you test the power switch as discussed earlier in thread?)

You don't even need to resurrect the machine to retrieve the data.

The machine I mentioned earlier where the PSU took out the entire machine failed again last week. It must be 10 years since I rebuilt it. I got as far as checking the mains lead was still live, said feck it, pulled out the hard drive and binned the machine. I just can't be arsed any more. I have better machines in the junk pile at work, I can just put my drive in one of them and be working again.

As said-

Tried onboard graphics port and working graphics card from another machine

Tried different monitors and cables.

Yes switch is fine

I have over 25 years experience building and fixing computers and in my professional opinion you've exhausted all possible combinations of logical troubleshooting.

I think you now have to consider ley lines - move the pc into another room, voodoo curses -try passing the bad vibrations from the computer onto someone you dislike, and engaging a professional to fix this.  https://sheikh-momo.com is able to break curses and remove negative energy. I suggest the Sheikh as your next action because all else has been done. Good luck Mr Potato!