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?
Who is Participating?

[Product update] Infrastructure Analysis Tool is now available with Business Accounts.Learn More

I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

dbruntonQuid, Me Anxius Sum?  Illegitimi non carborundum.Commented:

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.
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
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?
Determine the Perfect Price for Your IT Services

Do you wonder if your IT business is truly profitable or if you should raise your prices? Learn how to calculate your overhead burden with our free interactive tool and use it to determine the right price for your IT services. Download your free eBook now!

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?
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.
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.  

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today

From novice to tech pro — start learning today.