Computer powers on but no POST

Sniipe · 21-10-2010 1:01pm #1

The computer powers on but doesn't POST and doesn't have any bios beeps.

If a computer doesn't POST or beep what could the problem be?

Since the computer powers on it couldn't be the power supply.
Since the computer doesn't beep it can't be the RAM - because I've seen bad ram get as far as the POST screen.
Since the computer doesn't POST it can't be the bios battery - because even a dead battery would show that the battery is dead and datetime would be defaulted.
Everything is plugged out from the computer. I have seen a case twice when for some reason the external hard drive won't even allow the computer to POST.

So all that is plugged in is the power and I'm getting no beeps. I have access to another power supply so I'm going to try that first, but what else should I try?

I have unplugged the RAM, graphics card and other cards and re-inserted them hoping for magic, but nothing has happened.

The computer wasn't extremely dusty but I gave it an extremely light hovering.

Its a Dell XPS 710 - http://www.adverts.ie/showproduct.php?product=234738

Paulw · 21-10-2010 1:18pm

For me, when this happened, it was the graphics card that had died. I worked this out by using a different graphics card.

Or, it could be the motherboard itself.

Adam · 21-10-2010 1:55pm

i would guess it's the processor, but try disconnecting anything connected to the mobo internally as well if you can, i.e. usb ports front and rear, sound ports, card reader etc.

Sniipe · 21-10-2010 2:14pm

ok - so normally if I disconnect everything from the motherboard; graphics, cards, ram, fans, connections to internal card reader, usb, etc and only have the power and CPU connected, would I get bios beeps?

I had another look at the motherboard at lunch and it has 2 power connections to the motherboard from its 750watt PSU. I was going to try and put in my old 500watt one, but it only has 1 power connection to the motherboard.

Its a Q6700 and I have a Q6600 in my other machine, so if needs be I can swap processors.

PaulW, were you hearing any bios beeps when your graphics card was faulty? I find that confusing.

Paulw · 21-10-2010 2:22pm

No, the MB won't POST without everything connected (processor, RAM, graphics).

I heard no beeps when the graphics card died. The machine powered on, but nothing more - no beeps, no POST, nothing.

InquiringMind · 21-10-2010 2:29pm

If there are no beeps chances are your motherboard is dead. The motherboard should beep to indicate missing processor, ram, graphics card, etc.

Sniipe · 21-10-2010 2:31pm

Now that is conflicting to what PaulW has said...

marco_polo · 21-10-2010 2:48pm

Do you have these diagnostic LEDs on the front of your 710?

http://support.dell.com/support/edocs/systems/xps710/en/SM_EN/adtshoot.htm#wp1057135

Incidently in the beep codes I don't see anything listed for a Graphic card error so perhaps the XPS bios doesn't beep on graphic card failure.

subway · 21-10-2010 2:54pm

what exactly do you mean it powers on, but doesnt POST?

if the PSU fans are spinning up but nothing else happens on the MB then it could easily be dead PSU or MB.
if it hangs during POST, what stage is it at?
if it completes POST what stage does it actually get too?

the power button led should be your primary indicator if its getting power, but doing nothing else
similarly, dells generally dont beep, they have 4 status LEDs on the back that show whats going on if successfully starts POST

Sniipe · 21-10-2010 3:01pm

marco_polo wrote: »

Do you have these diagnostic LEDs on the front of your 710?

http://support.dell.com/support/edocs/systems/xps710/en/SM_EN/adtshoot.htm#wp1057135

Incidently in the beep codes I don't see anything listed for a Graphic card error so perhaps the XPS bios doesn't beep on graphic card failure.

The LED's are there (front of this machine), but there is no lights on them to indicate anything. Similarly there are no lights at all to the front of the machine (ie power button or the fancy lighting on the front of these xps 710's). Literally the only thing lighting up is the solid amber light on the motherboard.
And the only sound that is occuring is the fans. These Fans come on when you plug in the power, without switching the machine on.

I have to hold down the power button on the front of the machine for 10sec to turn it off and retry.

Sniipe · 21-10-2010 3:05pm

Its sounding more and more like a dead motherboard / PSU over anything else.

I'm going to try another graphics card next. After that I don't know where I will get these Dell M/B's or PSU's. They are not normal ones.

marco_polo · 21-10-2010 3:25pm

As the fans start spinnning when it gets plugged in, what eactly happens when you hit the power button? Is it then that the amber light comes on?

Sniipe · 21-10-2010 3:38pm

When the computer is unplugged - nothing is on

I plug in the power - the computer automatically revs up the fans then normally turns off (a 2 second operation). But now, instead of turning off they stay on. The amber light is on steady in the motherboard and there are no other lights.

I have only 1 option; hold down the power button at the front for 10 sec. Once off, hit the power button again and the same thing as above happens; fans start and stay on and the amber light is on the m/b.

marco_polo · 21-10-2010 4:17pm

Hmm it does sound like there is something wrong with the power up sequence, either the motherboard is not sending the power up signal to the PSU, or the PSU is not responding to it.

Just to fully rule out that it is not a power switch malfunction (I don't think it is as power off seems to be working correctly), could you unplug the power and reset switches from the motherboard and then power up the pc by shorting the two pins that the power switch was plugged into with a screwdriver (completely safe as this is exactly what the switch does, the motherboard recognises a short grounding of the pwr_on line as the signal to instruct the PSU to power up. And the voltages are miniscule)

EDIT: maybe re-seat the the 20/24 pin ATX power connector as well as this is how they talk to each other.

EDIT2: One other thing Fans that normally turn off after two seconds, are they case fans and are they connected through the motherboard or the PSU?

subway · 21-10-2010 4:18pm

its mothboard, possibly processor, but replace motherbaord first

Mr. Presentable · 21-10-2010 4:30pm

If you put your ear close to the psu when on, can you hear a high-pitched sound?

subway · 21-10-2010 4:53pm

solid amber led on the 710 means power is functioning, data is not being processed.
its a motherboard fault with a possible processor fault (unlikely)

that assumes that the OP has removed all components and still has the same issue

flashing amber is a PSU fault

marco_polo · 21-10-2010 5:21pm

subway wrote: »

solid amber led on the 710 means power is functioning, data is not being processed.
its a motherboard fault with a possible processor fault (unlikely)

that assumes that the OP has removed all components and still has the same issue

flashing amber is a PSU fault

All the amber light tells you about the power supply is that the motherboard is receiving 5VSB standby power, it could still be the PSU because it may not be responding correctly to the PS_ON signal from the motherboard which turns on all of the main power rails (3.3V, 5V, 12V etc.).

subway · 21-10-2010 6:37pm

marco_polo wrote: »

All the amber light tells you about the power supply is that the motherboard is receiving 5VSB standby power.

if you say so, my moneys on the MB

Sniipe · 21-10-2010 8:14pm

I will try what Marco Polo says. If its m/b how do I get a replacement? Would I just buy a normal m/b... what about my custom PSU that comes with it?

I'll also have a listen for the noise.

Thanks for helping me troubleshoot.

subway · 21-10-2010 8:22pm

im not sure about the psu, i guess it would be standard BTX and you could test the board with any you have lying around. marco polo might update you on what to do if the PSU is whistling.

however, i think the only place you will get a replacemetn board is direct from dell.
could cost around 400eu based on some comments online,

you would be as well to get a new MB proc and PSU and salvage what you can at that price.

marco_polo · 21-10-2010 11:22pm

subway wrote: »

if you say so, my moneys on the MB

Oh I haven't ruled it out at all.

Sniipe wrote: »

I will try what Marco Polo says. If its m/b how do I get a replacement? Would I just buy a normal m/b... what about my custom PSU that comes with it?

I'll also have a listen for the noise.

Thanks for helping me troubleshoot.

If it is the motherboard then pretty much everything everything must go unless you find another BTX motherboard (The bios will also have to support the same chip).

Problem is that as well as the BTX motherboard, you also have a BTX case that an ATX motherboard will not fit into because all the IO ports and PCI expansion slots etc will not allign properly. It is likely the cooler will need to go too.
This is how different the boards are.

Strictly speaking there is no such thing as a BTX PSU as the wiring uses the exact same pinout as ATX 2.2. It may be a proprietory Dell one though I'm afraid I'm not certain, however google is suggesting it is a standard ATX PSU on a number of different sites? If so and it is broken it would be directly replacable, or if not could be salvaged for a possible new build.

marco_polo · 21-10-2010 11:51pm

Sorry for getting your hopes up, I was wrong it is custom dell crap :mad: because it comes with both 20 and 24 pin 12V power connectors both of which must be pluged into the motherboard.

It cannot be replaced by an ATX PSU as they all come with a single 20(+4) connector. It also appears to lack the 4/8 pin 12V CPU connector that regular ATX boards use (The second standalone 20pin connector appears to perform this function for the XPS :rolleyes:).

You are in what is termed 'Dell Hell' in the PC upgrading world.

Sniipe · 27-10-2010 10:33am

Thanks for all your help guys. No more dell hell for me. I bought a new icore5 machine. It was for my parents.

I reckon the dell xps 710 was almost the same size as the cubby hole in the desk. The desk was also close to the wall. Because of these I imagine the machine overheated.

I won't be buying a dell again for myself or my parents.

I will try and sell the computer as is - ie broken. I doubt I'll be able to sell it.

Computer powers on but no POST

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