Monitor not turning on 4/5 motherboards

January 24, 2011 at 17:39:34
Specs: Windows Xp
HI so im confused about this.

I am fixing my friends computer that wouldn't turn on. I have a few spare motherboards and a spare psu. Turns out the psu was dead.

Now with the spare psw 230w the mobo will turn on. But the monitor wont turn on. Tested on 2 monitors.

I thought that was strange, so I tested the monitors on 4 other motherboards and they wouldn't turn on. 3 motherboards are using onboard graphics, and 1 is using a video card. The monitor's will however turn on with my newer computer.

The motherboards that wont turn the screen on are old (but still working) using intel p2 and p4 cpu's. The one that will turn on the monitor is a more recent computer with its own psu (unfortunately my new psu has more pins and cant be tested on the old boards).

So im confused... the common problem with everything that doesn't work, could be the 230w psu, but still turns on the motherboards. Could the psu turn on the motherboard but not power op the on board graphics ? if so even on my old intel p2 ?

I cant get hold of another old psu without buying one.

Hope that make's sense. Any suggestions ?


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January 24, 2011 at 17:53:22
I think you are making a lot of incorrect assumptions there.

What makes you think the motherboard is operating if there is nothing on the monitor. The fact that the fans spins mean very little except that there is some power getting to the mother board.

It is probably the PSU that is at fault. PSUs supply a variety of voltages. Even if you check the voltages with a voltmeter and they appear correct it still doesn't prove the PSU is working properly as it gives no indication of how the PSU performs under load,

It is like a motor car engine that will start and run on tick-over. But as soon as you put it into gear and try to accelerate it starts coughing and spluttering. Power supplies can behave in the same way.


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January 24, 2011 at 18:38:17
Thanks for the fast response. Could I plug my 24pin psu into the 20pin motherboard ?
While letting the end 4 pins hang over the end. Or would it not power up properly ?

At least I know I know that psu works.


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January 24, 2011 at 18:56:32
You can use the 24 pin PSU and just leave un used pins hanging lose. They provide extra power for more powerful CPU and graphics cards.

The lines that are used during the power up process, basically the green and the gray one, are in the first 20 pins that are common to all ATX motherboards.


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Related Solutions

January 24, 2011 at 20:14:21
I plugged in the 24pin psu, but I still cant get anything to come up on the screens. I tried on 3 motherboards one of them had capacitors in the way.

What would you try next ?

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