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HELP!!! My computer won't turn on!!

Kevlar

Kevlar

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Ok. I've had a PSU fail on me before, so I got a new one, hooked it up and everything was fine for about 2 years.

Then the other day I turned my system off and now it will not turn back on!!! So I thought, probably another bad PSU, so I ordered another, hooked everything up and... nothing.

So I'm hoping someone could help me. I took out my DMM to test the PSU and it reads nothing. I tested the motherboard connector off of the PSU and some of the 4 pin molex connectors, nothing. I could very well have set my DMM wrong too. I set it to 20V in DC mode, is this correct? My cheap DMM, on the lowest AC voltage will only go down to 200V. I thought the 4 pin motherboard connector was 12V.

I was also searching online and a few places it stated to hook up the PSU and see if the power LED on the motherboard lights up. Do they mean there is actually a LED on the motherboard itself? Because if that's the case, I can't find it.

My system is a HP Media Center m1180n. Motherboard: ASUS PTGD1-LA.
LINK: Motherboard Specifications, PTGD1-LA (Puffer) HP Media Center m1180n Desktop PC - HP Customer Care (United States - English)
 





Ignis Fatuus

Ignis Fatuus

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The Molex plugs are 12v. It may or may not have a LED on the board. You need to put a load on the PSU and test the outputs.


connector_atx_pinout.GIF
 
Kevlar

Kevlar

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Ignis Fatuus said:
The Molex plugs are 12v. It may or may not have a LED on the board. You need to put a load on the PSU and test the outputs.

atx-psu.gif
Click to expand...

Ok, so please treat me as a noob with some kid gloves :eek: How should I put a load on the PSU to test the outputs?
 
goninanbl00d

goninanbl00d

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To test a PSU, simply use a wire to bridge the PS_ON pin (pin 14) to ground. The supply will not turn off till these pins are disconnected from each other.

Most modern PSUs can run fine without a load- and unless it's a generic cheap unit with shoddy circuitry to begin with, there'll be no harm done to the unit.

The 4 pin mobo connector is 12V and GND (yellow and black, respectively). The Molex connector is 5V, GND and 12V (red, black and yellow).

On most of these OEM motherboards, there is a PWR_ON LED for debugging purposes. If the motherboard is recieving power, then the light should be on. This light is usually on the lower right corner of the board.

If it is the power supply that's DOA, get a refund, and get a brand name unit. Sure, it'll be more expensive, but it'll be significantly less likely to die on you in a year. Look out for Corsair and Seasonic units, they're often regarded as the gold standard in desktop PCs.

Think of it this way- Can you get a 200mW green for $14? Well, can you get a '600W' PSU for $50 or thereabouts?
 
Ignis Fatuus

Ignis Fatuus

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Check the diagram below. The one on the left will be yours.

connector_atx_pinout.GIF


Hook a bare wire to the green wire and any ground. This should start the PSU.

images


If it doesnt keep going you are going to have to add a resistor. Get a Sandbar 10ohm, 10 watt resistor at RadioHack (under $1) and put it across the +5v supply.
 
Ignis Fatuus

Ignis Fatuus

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goninanbl00d said:
To test a PSU, simply use a wire to bridge the PS_ON pin (pin 14) to ground. The supply will not turn off till these pins are disconnected from each other.

Most modern PSUs can run fine without a load- and unless it's a generic cheap unit with shoddy circuitry to begin with, there'll be no harm done to the unit.

The 4 pin mobo connector is 12V and GND (yellow and black, respectively). The Molex connector is 5V, GND and 12V (red, black and yellow).

On most of these OEM motherboards, there is a PWR_ON LED for debugging purposes. If the motherboard is recieving power, then the light should be on. This light is usually on the lower right corner of the board.

If it is the power supply that's DOA, get a refund, and get a brand name unit. Sure, it'll be more expensive, but it'll be significantly less likely to die on you in a year. Look out for Corsair and Seasonic units, they're often regarded as the gold standard in desktop PCs.

Think of it this way- Can you get a 200mW green for $14? Well, can you get a '600W' PSU for $50 or thereabouts?
Click to expand...

Great advice, but let me finish answering his question first please. You're wasting my time.
 
A

anselm

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If the PSU checks out fine, it's either the motherboard (most likely) or the cpu. ;)
To check for the very unlikely event of the on/off switch having failed, pull its cable
from the mobo and short the two now exposed pins with something metal.
 
Kevlar

Kevlar

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Thanks for the help guys. :beer::thanks:

Well, I have bad news, and I guess, more bad news. I checked out both of my PSUs. The old one, which I thought was bad, is fine. Same with the new one.

So something else is wrong. I hope it's not the motherboard or cpu.

anselm said:
If the PSU checks out fine, it's either the motherboard (most likely) or the cpu. ;)
To check for the very unlikely event of the on/off switch having failed, pull its cable
from the mobo and short the two now exposed pins with something metal
Click to expand...

To rule out the on/off switch, I pulled the cable from the mobo and there are nine pins. Kinda looks like this ':::: Which pins do I short?
 
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anselm

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The pair that is connected to the on/off button on the front of the computer.
The wires should be colour coded so you can tell em apart from the wires for
reset and the power and HD LEDs.
Just gotta find the button and follow back from there. Sometimes its even
written on the plug itself or the moterboard.
Do all plugs come off together as one or individually?
 
Last edited:
S

SpyderFire

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Be careful when messing with power and your motherboard. You may end up shorting it and killing it., my suggestion would be for you to take somewhere so that it can be properly troubleshot.
 
Kevlar

Kevlar

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anselm said:
The pair that is connected to the on/off button on the front of the computer.
The wires should be colour coded so you can tell em apart from the wires for
reset and the power and HD LEDs.
Just gotta find the button and follow back from there. Sometimes its even
written on the plug itself or the moterboard.
Do all plugs come off together as one or individually?
Click to expand...

Thanks, I found them. I'll check this out tomorrow though and report back.

SpyderFire said:
Be careful when messing with power and your motherboard. You may end up shorting it and killing it., my suggestion would be for you to take somewhere so that it can be properly troubleshot.
Click to expand...

I'm taking some ESD precautions. Is there some other safety measures they use that I can? I just don't have the dough to pay for someone to repair it right now.
 
goninanbl00d

goninanbl00d

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If you can get one, then use an ESD wristband.

Else, leave the computer plugged in, and switched off at the mains (so you have a ground line).

Brush the back of your hand on an exposed part of the chassis when you want to ground yourself. Ground yourself whenever you move around, and before touching any exposed components.

It's most likely the motherboard itself, or the power switch. A screwdriver works fine- just bridge the two metal pins and your computer should come on.

At this stage, it's probably highly unlikely it's a CPU problem. With a dead or missing CPU, the motherboard will power on, but nothing will be displayed (no POST).

I'm leaning towards a motherboard failure, but I'm hoping I'm wrong :undecided:
 
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SpyderFire

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Kevlar said:
I'm taking some ESD precautions. Is there some other safety measures they use that I can? I just don't have the dough to pay for someone to repair it right now.
Click to expand...

What i meant was more along the line of , touching the wrong pin or metal contact on your board while power is on or attempting to be on, ESD protection cant help you there.

one thing you can do , is take out all the cards all the ram except one stick. then try to power it on. I've had a bad video card keep the system from powering on. Its always good practice to bring it to a barebones status then add parts one at a time.
 
goninanbl00d

goninanbl00d

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anselm said:
That right there is how it's done.
Click to expand...

Yes, that is the correct procedure for bench-testing.

At the current stage, given the current situation, tracing the power button back first is the most logical option.

If that does not work, then let the bench testing begin.
 
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