Problem changing power supply on Dell Precision 690 - 2 MB power connectors

Hi - I'm in the process of changing the power supply on a Dell Precision 690, and i have a problem - when unplugging all power connectors from the MB, i saw there was a second (P2) connector coming out from underneath the MB, so I have the normal (power1 - 24 pin) on the MB and this one P2 (20 pin). The NEW power supply i bought doesnt have a second power connector - does anyone know what this is for?
hodgemAsked:
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dbruntonQuid, Me Anxius Sum?  Illegitimi non carborundum.Commented:
See http://en.community.dell.com/support-forums/desktop/f/3514/t/17970830.aspx

From there it looks like one powers the CPU and the other the board.  The diagram referenced doesn't show the second power connection under the board though.
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kpmartinCommented:
It must be an extra 20 pin for MB that use that.  Most PS's have a 20 and a 4 so you can add them together for a 24 pin.  Some MB's have a 20pin and a separate 4 pin (or 6) next to the CPU.  The one you say was under the MB was just tucked there I suppose; never saw a MB that had a connector underneath.  I hope I'm understanding your description correctly!  kevin
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hodgemAuthor Commented:
Hi - apparently that connector is for the processor - BUT, now im having another problem. I purchased 2 power supplies, and connected the normal 24 pin to the MB, that 20 pin to the processor, the other connector to the cd drive, and its RAID, so i connected the othrer 2 to the HDs. For BOTH power supplies, when installed, the pc doesnt start up. Am i correct in assuming that as long as i have the 24 pin plugged into the MB, it should start?
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kpmartinCommented:
If you have both the 24 & 20 pin connected it should start up.  Do you get a power light on the front?  Do you get any error lights?
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hodgemAuthor Commented:
no power light, no error lights - the only thing i get is, as soon as i plug the PS cable into the wall, it makes a click sound. I also checked to make sure there wasnt an on/off switch on the PS itself, and there wasnt.
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kpmartinCommented:
I would try disconnecting the drives and if the result is the same then probably the MB is at fault.  The click you hear may indicating an overload and circuit protector activating (guessing).  You can often spot a problem like that on the board by looking for a burnt/charred power reg chip and/or a bulging capacitor top.  
kevin
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