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Is my mobo, cpu and psu fried, connected wrong cable, help

Last response: in Systems
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January 11, 2011 9:27:30 PM

Hi,
This is my first build, although I have done bits of building in college. I connected everything up and turned on the computer. After a few seconds there was a burning smell, and nothing displaying on the screen. I quickly plugged it out.

I know what I done wrong now, I had connected a 4-pin floppy power cable into a 3-pin fan connector on the mobo for the case fan. I thought the cable was for a 4-pin fan. The cable I connected has 2 black wires, a red wire and a yellow wire. I left the yellow wire unconnected. I believe this is what caused the burning. I now know that I need a molex to 3-pin adaptor to connect my case fan.

I wanted to see if the computer was ok after this happened so I took out the floppy cable from the mobo and just connected the case fan to the psu, with no connection to the mobo. I turned on the computer again, it will not boot, no beep signal, nothing on screen.

So my question is what components are fried? It seems that the mobo is dead. I tested the psu, and the -5v parameter does not seem to work, but I don't trust the PSU tester that i used as it is a cheap one. Could it have damaged any more of my components? e.g CPU, RAM, hard drive etc. What components do you think could be damaged?

I think my motherboard is dead and possibly the psu, and I will RMA these back to the retailer. But I dont know if my cpu is fried or not. Has anybody had experience of this happening before, and if so what components do you think are affected.

Grateful for any help or suggestions. Thanks!

Mobo: Asus P7H55-M
CPU: Core i3 540
HD: Samsung 1TB F3
Case: CIT Black Micro ATX 450W
RAM: ValueRam 4GB DDR3
January 11, 2011 9:36:09 PM

Could be the PSU and/or the motherboard.....
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January 11, 2011 9:38:15 PM

You have possible damaged your PSU and certainly the motherboard most likely the CPU escaped.
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January 11, 2011 9:51:30 PM

Thanks for the replies guys.

I arranged a RMA for the psu and mobo today, so they should be replaced. I hope you are right rolli59. I was worried the cpu was fried too!
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January 11, 2011 9:54:51 PM

You sent voltage directly from the PSU to a fan controller that gets supplied voltage through the motherboard independent of the CPU.
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January 11, 2011 10:16:07 PM

Thats good to hear. At least I can salvage some of the components then. Only thing I can do now then is wait for them to collect the psu and mobo and replace them. Their not collecting them til 26th. I'm very relieved to hear my cpu is ok anyway.

Thanks for the help guys!
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January 11, 2011 10:18:07 PM

Actually, I was also wondering how would that have damaged the psu? I don't get how it could have affected it. Unless it just damaged the floppy cable?
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January 11, 2011 10:22:45 PM

We do not know about the PSU but we know for sure what you did is not good for it and therefor possibly damaged voltage regulation inside.
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January 11, 2011 10:28:17 PM

Yeah, that would explain why the -5v parameter wasnt working correctly when I tested it. Its no harm to be on the safe side and replace it aswell. Otherwise it could damage the new mobo I get.
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January 12, 2011 3:40:06 PM

The -5V line likely doesnt even exist on your unit, it is no longer necessary as nothing on a modern board connects to it so it has been dropped from the ATX specs, and from the 24 pin main connector on most units.
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January 12, 2011 5:10:06 PM

Ah right, I didn't know that. Yes, there was no -5v on the 24-pin connector alright. Maybe the psu is fine then. However, i may reuturn it just to be on the safe side. Thanks for the info hunter315. Does anyone know if my RAM would be affected by what happened?
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January 12, 2011 6:52:48 PM

Very unlikely as per my CPU statement above.
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Best solution

January 12, 2011 8:02:27 PM

It wouldnt have made it that far, it probably cooked the PWM module on the board but wouldnt have been able to make it back very far, the main connector would have been providing higher voltage that would have stopped any damage. The RAM is powered off of the 3.3V rail from the 24 pin main connector, it would be electrically isolated from the fan header so you wont have damaged it.
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January 13, 2011 2:39:04 PM

Ah yes, I understand what you mean. At least I'm safe in the knowledge that they are ok then. Thats put my mind at ease. Thanks for the help everyone.
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January 13, 2011 10:55:56 PM

Best answer selected by davidom2513.
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December 20, 2011 4:57:29 PM

Hi,
I´ve just made very similar mistake - I connected CPU cooler to case fan connector on motherboard (I connect it without thinking to nearest connector as usual) and result was only burned power supply...
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