Faulty PSU or M/board plugs?

  mrwoowoo 21:47 PM 22 Jan 13
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Installed m/board,new Ram and CPU in sons PC. Fairly sure it was working ok. Then he decided he wanted a new PSU so he could upgrade his GPU to my old one. Installed a new 700w PSU, and now when you turn it on it goes on and off very quickly , usually 3 times (about every 2 seconds) without the monitor having time to come on. Once it's on though it runs well,even with long periods of playing new PC games. Very occasionally it may start first time. I know that with the reset and power switch on the m/board, the polarity shouldn't matter as they only need to complete a circuit.Or could they cause these sympoms? The other strange thing is that the power light on the case doesn't come on. I'm fairly sure i plugged them all in correctly as they are clearly marked. My only doubt is with the power swith and reset switch, as on the m/board header there is a dummy pin slot, although ,again i'm fairly sure i didn't use it. Should i just return the PSU to Maplin? I know i could just swap back the PSU, but time will be tight on Saturday when i get there as Maplin is a fair way away, so i need to know what to expect,and what the possibilities are. The M/board is an Asrock pro4-m

  alanrwood 22:53 PM 22 Jan 13

It may be that you have incorrectly connected the front case connectors and you have somehow shorted the Reset contacts so it boots and immediately resets. The fact that you also have no power light leads to the same conclusion. Look in the M/B manual and ensure they are correctly connected. There should be a diagram of the connections in the manual but sometimes they are so small they are difficult to read. To confirm just disconnect every connection except the Power on/of, which as you say just shorts two pins together to signal the PSU that it should start up.

Also check that the second PSU connector is well seated on the M/B.

  mrwoowoo 00:05 AM 23 Jan 13

Thanks Alan. Just to get it straight in my mind. If i do just leave the power swicth in place, what will i expect to see when i power up if, A. it has been wrongly connected, or B. it hasn't been wrongly connected. Also, what if i just disconnest the reset switch? Would that sort it?

  alanrwood 09:16 AM 23 Jan 13

Hi If you just have the Power switch connected and the others disconnected then if connected correctly the computer will power up and act as normal except you will not have the Power LED light, the reset will not work and the Hard Drive LED will not work. None are essential to the working of the computer. If not connected correctly the computer will not power up at all. I suggested all except the power wires simply to ensure that you had not incorrectly installed any of the others. If the computer works as it should you now know what was causing the problem and can recheck that the others are installed correctly. To be honest I always enlarge the drawing in the motherboard manual so that I can read it easily. It is also easy to think it has been installed on the correct pin and find that it has not so been installed, they are so fiddly. Can't actually tell you which pins to use for what as it changes between motherboard brands and models.

  Chronos the 2nd 09:22 AM 23 Jan 13

Do you have the 4 pin ATX power connector inserted? I know it is a perhaps daft question but it would not be the first time I have forgotten or not connected it firmly.

  mrwoowoo 16:33 PM 23 Jan 13

chronos Yes i plugged the 4 pin ATX power connector where it should be according to the manual. Though i did almost forget LOL. Looking at the manual i have found another diagram that has a line from the p/switch and reset to there positive and ground plugs. These go across the header as opposed to vertical like all the other connectors. Not sure if it would make a differance as it's still just positive and ground/negative in both cases. Anyway. I will take a look and implement your advice and let you know the result.

  mrwoowoo 19:12 PM 25 Jan 13

Oh dear!

Well that must have been the worse attempt at installing a M/board that i have ever done. And i've done a fair few. Although my eyes arn't what they used to be. lol! The power LED pins had come out. Probably when i was connecting the numerous other wires in the case. Also, the power switch and reset pins were in the wrong place. Heaven knows how i managed that. At least it wasn't the new PSU,M/board or CPU that he bought. Thanks alan. You were right about the pins. All sorted. !:O)

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