trying to make a power supply for some case fans

[loveturtle]

apparently the power supply in my case cant supply enough juice,
I got an old transformer here that outputs 12VDC and 300ma
the fans have 3 wires red black and I am unsure of what the yellow one does
also would like to hook it up to some of my other cooling devices that run on the four big wire hookups
red black black yellow,could someone out there please explain to me what all the wires are?

 

[AC]

on the 3-pin fans, the yellow wire from the fan is just RPM monitoring, just disregard since u can't use it with your fan PS

on the 4-pin connector, the red wire is +5 volts, the 2 black ones are both ground, and the yellow is +12 volts

 

[miniMUNCH]

Don't waste your time...300 milli-amps (0.3A) at 12VDC will only give you 3.6 watts. Upgrade your power supply.

As for the Red /2 Blacks/Yellow thing (don't quote me on this):

Red - 5V *edited* positive (power source)
Yellow - 12V *edited* positive (power source)

The blacks are your COM wires...like a neutral on an AC circuit...one COM for the 12V and one for the 5V.

Edit: I had the red and yellow voltages switched around

 

[loveturtle]

I tried it out with 2 of the fans and it works good,I am going to get another transformer that can handle more power and hook up my hd cooler and all the fans to it
forget about getting another power supply,this one is brand new 300W
I think this transformer thing is the way to go
thanks for the information