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new pc did work now doesn't, please help

by rjob / March 4, 2005 3:15 AM PST

i have just finished building a new pc, turned it on for the first time yesterday and it was working fine. came today to turn it on and nothing, i've taken out all the connectors and rechecked them but nothing, all that happens is the led on the motherboard turns on and the psu makes some sort of noise (not the fan) but it doesn't power up at all which i find surpising as it was fine for the few hours i had it on yesterday.

the specs.

asus k8n motherboard
amd64 3400+
1gb ddr
2 sata 160gb hdd
peak radeon 9550 graphics card
sony dvd+/-rw
400w psu

think thats it, please help

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reply
by AInTeL / March 4, 2005 3:28 AM PST

Dear rjob,

Try using a different power supply, to see if it's still operational - that's a common problem. It's also usually possible 400W isn't enough to run some Asus motherboards, but considering it has worked recently, that shouldn't be your problem.

You have an excellent computer system, so there shouldn't be any problem whatsoever, so if something's faulty, then don't hesitate to exchange it - expensive hardware should be running perfectly.

Let me know what was wrong with it,
-AInTeL

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re: reply
by rjob / March 4, 2005 11:18 PM PST
In reply to: reply

the only other psu i have my hands on is 215w, which won't really do. may try the 400w psu in the system that has the 215w one in. did i mention this is the first pc i have built from scratch

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re reply
by rjob / March 4, 2005 11:20 PM PST
In reply to: reply

the parts came from different internet stores, i really need to know if there is a faulty item or something i have done wrong before i start sending stuff back.

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you need to do more work
by ahmer_sahab / March 7, 2005 8:29 PM PST
In reply to: reply

Hi rjbob,
What I think, you check your motherboard manual for power requirement. The problem could be your power supply is not providing enough voltage to motherboard. My friend had same experience too, Its strange but when we changed the RAM. The system started working perfectly. So try both of things and let me know if it worked or not. I am waiting for your reply

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PSU
by PlatinumPPC / March 4, 2005 3:32 AM PST

What's the PSU brand?

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re: psu
by rjob / March 4, 2005 11:12 PM PST
In reply to: PSU

it is the psu that came with my case, the logo looks as though it says colors

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Just for your info. The LED
by Ray Harinec / March 4, 2005 3:44 AM PST

on the mobo is norma;lly an indication that the 5 volt stndby power is on. With ATX systems this is always there as long as the power supply is plugged into a hot outlet.

If it isn't on all the time, how are you turning the system on??? If you do it by plugging the supply in, you may be causing the turn on logic circuitry to get confused, because of a setting in the power management section of the BIOS..

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re: Just for your info. The LED
by rjob / March 4, 2005 11:11 PM PST

i have unpluged the system to check all the connections etc. is there anything i can do to check this, i can't get into the bios cos i can't turn it on.

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re Just for your info. The LED
by rjob / March 4, 2005 11:24 PM PST

thinking about this, the problem did first come about after i unplugged the pc to move it into another room, but this soon sorted itself out and i was using the pc for a few hours, before i turned it off (via 'turn off computer' in xp)

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Is the LED on the mobo illuminated???
by Ray Harinec / March 4, 2005 11:33 PM PST

If not, that means that the power supply is not providing the 5 volt stndby power that is needed for the mobo to turn the rest of the power supply outpu5ts [rails] on.

Check that the switch on the rear of th Power Supply is in the 1 position, and that the proper voltaqge is selected.

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re Is the LED on the mobo illuminated???
by rjob / March 4, 2005 11:40 PM PST

yeah the led comes on, so there is power coming through, can't see a switch for the voltage, but there is a sticker on the back that says 230v so i assume that that is what it is set at

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Remember, that is only for the
by Ray Harinec / March 4, 2005 11:55 PM PST

5 volt standby voltage. That powers the logic circuitry on the mobo that enables turning the real power on by a momentary contact front panel switch.

Any chance that the 4 pin 12 volt connector that powers the CPU has come off or loose???

Is the 20 [or 24] pin connector on the mobo connected fully???

Where are you located that 230 volts is your power source???

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i'm in the the uk
by rjob / March 4, 2005 11:58 PM PST

i have checked all the connections, i have even tried to run it without any of the case fans and dvd rw drive connected so reduce the power needs. i just don't understand how it was working one day and not the next. is it worth completetly taking it apart and refiting everything?

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Just a dig. That's the normal way to build
by Ray Harinec / March 5, 2005 12:24 AM PST
In reply to: i'm in the the uk

a new PC. One step at a time and check after each step.

Some even start with the mobo on a piece of cardboard to insure that it isn't shorted to the case. LOL

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Some of the better new power supplies
by Ray Harinec / March 4, 2005 11:57 PM PST

automatically adjust for the input voltage from 230 volts down to about 80 volts. Maybe you have one such.

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Can you further explain
by Ray Harinec / March 5, 2005 12:01 AM PST

"this soon sorted itself out" Might be a big clue.

BTW it is not unusual for the power supply that comes with the case to be a low line supply, bought from a low bidder.

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re: can you further explain
by rjob / March 5, 2005 12:06 AM PST

when i moved it into another room it would not turn on, i opened the case checked all the connections and low and behold it worked again. sadly this has not been the case this time. i was planning on a new power supply, but just wanted to get it up and working first, and as i say it was working before so i really don't understand what is going on

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No chance that you have the CMOS jumper
by Ray Harinec / March 5, 2005 12:20 AM PST

on the wrong pins?? [would have to have been done after the last time it worked]. Weren't trying to update BIOS ???

Get stripped [the computer that is] to simply the mobo, the power connectors, one stick of memory in the slot 0, the CPU with HSF plugged in. Keyboard, Video, and monitor, all of the font pnel connections and the Speaker. [BTW did you get a single beep when it worked?].

No drives connected, neither power or ribbon cables, no floppy.

Turn power on, what happens?

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haven't changed any jumpers
by rjob / March 5, 2005 12:23 AM PST

can't remember a beep but not sure on that i'm afraid. no drives include hard drive?

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Yes, no drive includes hard drive.
by Ray Harinec / March 5, 2005 12:32 AM PST

You are operating in the BIOS operating system mode. The hard drive can't do anything but hurt at this point.

You can actually turn the supply on with no memory, no CPU, nothing connected except the PS to mobo connections, then momentarally short the Power on pins on the mobo together with the tip of a slot screwdriver blade. All of the rest of the stuff is window dressing. Can't get this far, why waste time with anything else.

Your case is different though because you lucked out and it did work with a all in one step assembly.

The noise from the Power supply is sure suspicious. Have you put your nose close to take a whiff. Possibly lost some capacitors in it.

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tried that
by rjob / March 5, 2005 1:19 AM PST

still nothing. the sound is still there from the psu, can't smell anything. after i turn off the switch to the power supply it takes a while for the noise to go and for the led to turn off, is this normal? does it sound as though it is a faulty power supply?

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reply
by AInTeL / March 5, 2005 1:43 AM PST
In reply to: tried that

rjob,

Test the power supply in a different computer, or get another to test in with this system.

Chances are that it's the supply, so it would be much faster to just test it.

-AInTeL

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He can give a simple turn on test
by Ray Harinec / March 5, 2005 1:50 AM PST
In reply to: reply

independent of any computer.

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the only other
by rjob / March 5, 2005 3:00 AM PST
In reply to: reply

don't have another atx psu

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I have no idea why the noise would
by Ray Harinec / March 5, 2005 1:48 AM PST
In reply to: tried that

take a while to go away, but the light taking a while is simply that there are some cpacitors charged to that voltage and it takes a little time for the charge to bleed of.

If that PS fan doesn't turn on with the mobo power plugged in, it is either the supply or the mobo. Most likely the supply.

I could tell you how to check the power supply by itself [unplugged from the mobo] if you would like. Most likely a waste of time though.

Let me know.

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if you can tell me
by rjob / March 5, 2005 2:58 AM PST

how to check that would be good, then i will know 100% that it is the psu and not the mobo, i got them from differrent sites so i need to know which one to send back. is there no chance it could be anyhthing to do with the switch on the case or the cpu? the power supply for my laptop has just gone this afternoon as well; not having much luck.

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OK. First I must know whether the
by Ray Harinec / March 5, 2005 3:16 AM PST
In reply to: if you can tell me

power connector to the mobo is 20 or 24 pins.

Then I will tell you how the pins are numbered and what two pins that you will jumper together.

We will be working form the rear of the connector. Those molex connectors have a lot of slop in them so it is easy with thin metal, maybe a samm paper clip [straightened. LOL]

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there are
by rjob / March 5, 2005 3:19 AM PST

20 pins

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form = from and samm = small. My typing
by Ray Harinec / March 5, 2005 3:19 AM PST
In reply to: if you can tell me

in a hurry stinks.

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OK the pins down one side
by Ray Harinec / March 5, 2005 3:35 AM PST
In reply to: if you can tell me

run from 1 to 10. Down the other side from 11 to 20. Pin 11 is next to pin 1, thus pin 20 is next to pin 10.

Remember, this is done when not connected to the mobo [can do it with a new supply in the box if you plug it into the wall]

To figure out which row is 1 to 10 and which 11 to 20, look for the black wires [these are all grounds [also called commons]. On the 1 to 10 side there are only three black wires, four black ones on the 11 to 20 side. Pins 1 and 11 are 3.3 volts [also pin 2] and are normally orange. Pin 10 is 12 volts [usually yellow] Pin 20 is 5 volts [normally red.

Your simple task is to put a logic low on pin 14. Sounds important doesn't it? LOL

Simply means to connect pin 14 to any one of the black ground pins and keep them connected. If you are sure that the jumper is making good contact at both ends the power supply fan should turn on.

BTW you can go to cyberguys and buy a simple device to do this and it has an LED that will light. LOL It DOES NOT test the power supply under load just has an OR circuit to show with one light that all voltages came on. It's so inexpensive that you have to order something else because it does not exceed their minimum ordering amount. LOL

Good troubleshooting and lets get this system working. Let us know when it is working. We really care.

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