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When your system won't start.

By m.franklin2 ·
Many of us have been there. You press the power
button, and nothing happens. I'm there now. What do
you do to recover, and prevent it from happening
again?

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Prevention

by TheChas In reply to When your system won't st ...

Things to prevent / limit system failures:

An adequate or over-sized power supply.
I don't use less than a 300 watt supply anymore.

Cooling, Cooling, Cooling!!!
Install a good CPU fan.
Install case fans blowing air in so that the case has a slightly positive air pressure.

Cleaning.
Clean the inside of the case and ALL air vents and heat-sink fins at least once a year.

Surge Protection.
Surge protection is not just for lightning storms. Any number of events can cause a voltage surge on the power line that can damage the power supply or the motherboard.
Install a good surge protector, and make sure that you have a good ground for the power line.

Modem lines.
Many times in a storm, the surge that does the most damage comes in through the modem, cable, or NIC line.
Make sure that ALL external connections have a fuse protected surge suppressor.

Chas

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Trouble-shooting

by TheChas In reply to When your system won't st ...

Actually, the trouble-shooting part of this belongs in the Technical Q&A section.

NOTE: If you search the articles here at Tech Republic, you will find a few step by step guides on power supplies and dead system checks.

Start by verifying the power supply.
On an ATX system, there is a 5 volt line that always provides power to the motherboard. This runs both the real-time clock, and the power control circuit.
Most modern ATX motherboards have an LED that signifies that the 5 volt standby power is on.

Otherwise, if you know how to use a voltmeter, you can look at the ATX power connector pin-out and check the 5 volts there.

If 5 volts is NOT there, most likely the internal fuse in the power supply blew.
CAUTION: even with power off, there can be high voltages present inside the power supply.
You are best off to swap in a known good power supply.

The power on sequence for an ATX system is:

The front panel power switch is a momentary push button switch.
Pressing the button closes a circuit that signals the power control circuit to tell the power supply to turn on.

Once the power comes up, the power control circuit sends another signal to the power supply that all is well and keep power flowing.

Any number of component failures can cause a no power condition. The power control circuit, the CPU, even on-board voltage regulators can fail and cause a no power situation.

Take a close look at the motherboard. You are looking for bulged, burnt, or charred components. If you see any, the motherboard will need to be replaced.

For AMD socket A CPUs on motherboards with SDRAM, I have seen a no power condition if the CPU speed was set too slow.
Try resetting the CMOS and see if you can startup then.

From here on, it's component swap time.
Start by disconnecting ALL plug-in cards. If the system now starts, one of the cards is bad.

Swap RAM, CPU and video card.
If it still does not power up, the motherboard is the likely suspect.

Chas

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Just to clear up something that The Chas missed

by HAL 9000 Moderator In reply to Trouble-shooting

Or more likely didn't think about when you look at the M'Board there are little electrolitic capacitors they look like little cans that are soldered to the M'Board somewhere around the CPU. These if they are not of the right spec can fail and they can either swell and burst or break their connection to the M'Board. If you see any swelling on any of these parts junk thre M'Board as you can not replace them.

The rest about burnt or chared bits stands but look very carefully at those capacitors first as they are quite often the first thing to fail which stops the voltage reaching the CPU.

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Cap Failures

by TheChas In reply to Just to clear up somethin ...

Colin,

I am aware of the cap failure issue. I just didn't go into that level of detail.

About a year ago, there was a rash of motherboard failures that were the result of some bad electrolytic capacitors from China.
Turns out someone stole the formula for the electrolyte, but did not get the complete formula.
The result was a batch of unstable capacitors.

You are correct that any bulging or liquid leaking from an electrolytic capacitor is a cause for concern.
It has been quite a while since I saw an electrolytic explode though.

In the 80's, I worked on stereo equipment. The tech who sat next to me was in way too much of a hurry. About once a day, he would **** up an amplifier.
It got to the point where he would duck under the bench when he powered up any unit he repaired.

Chas

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You'll just love this one

by HAL 9000 Moderator In reply to Cap Failures

Over here in AU about 25 years ago there wasn't mains power throughout the country so a lot of farms out in the bonnies used 32 V equipment. Now the 240 V switches where about 1/3 the price of the 240 V stuff so guess what was normally fitted to these 32 V installations?

You've never seen anything until you plug in a 32 V sewing machine to 240 V and run it flat out. It picks itself up off the work bench does about 3.5 backward flips and then crashes down to the bench of course you **** the 32 V bulb as well but it is specatular and best of all most of these mods didn't have a 32V notice on their specification plate so you never knew until the thing jumped at you.

But speaking of Audio Caps remember those big ones that would hold a charge for hours after powering down and exactly what they used to do when you let someone pickup a charged one?

But I'm a ******* really as I used to do this to anyone who stuffed up constantly they never knew exactly what they could touch and when but at least they worked a bit slower and did less damage.

Any way Happy New Year Mate and keep up the good work.

Col

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Remove NIC

by Oz_Media In reply to When your system won't st ...

I'ce had two PC's in the last two months that seeemed completely dead when tha poser was turned on.

As soon as the (faulty?) NIC card was pulled they BOTH came to life.

Try pulling the cards and see if you can get booted.

Good luck!
OM

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are all the wires connected to the front panel ?

by lawrephord145 In reply to Remove NIC

are all the wires connected to the front panel ?

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