Replacing Power Supply

[galaxy]

I am replacing a power supply on a motherboard.

The one that i am taking out has a long strip of 20x2 wires and a smaller block near it of 2x2 wires.

The power supply i am replacing it with has the 20x2 but not the 2x2. it has a 2x3 that wont fit.

What does this bit do and does it matter it i dont plug anything in to it.

[JimmyK]

I believe that the extra connection is for the power supply fan.
In the case of the 2 wire version, I suspect it is a tachometer to monitor the speed of the power supply fan.
I think the 3 wire version is a version which would allow control of the power supply fan (2 of the wires) and also monitor the speed (the third wire).
I would hope that the fan in the power supply runs regardless of the 3 wire version being connected: you can safely test it by switching on for a couple of seconds to see if the fan runs. If it does then you are OK, if it doesnt then switch off immediately before any excess heat builds in the power supply.
As an alternative to my guesses, is there no information with the power supply to tell you? Or can you get info from the net (if necessary using another computer) to find a data sheet?

[kempie]

On ATX power supplies the 2x3 block is usually additional power for system fans and firewire peripherals, while the 2x2 block (or 4 Pin Molex P4 12V Power Connector) is specifically for use by Pentium 4 processors.

Assuming you have a P4 processor, I am not sure if you can run your motherboard without the P4 12V connector attached. If this is the case you may need a 5.25" HDD Molex (1x4 block) to P4 12V converter, such as this...

http://cgi.ebay.co.uk/MOLEX-TO-P4-64-BIT-CONVE RTER-CABLE-4-PIN_W0QQitemZ220014369408QQihZ012 QQcategoryZ45342QQrdZ1QQcmdZViewItem

[galaxy]

OK. I managed to find another power supply that had the 2x2 pin on it.

The PC boots up fine but the problem now is when i power it down, there is a constant clicking noise coming from the power supply and the amber light on the front of the pc is flickering. The only way to stop this is to turn it off at the wall (or remove the cable!)

Is this dangerous, causing a problem or will it simply just be annoying.