Svenska ElektronikForumet

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where the top spikes are the key tabs on the connector. Pin 1 is ground, pin 2 is 12V power, pin 3 is the Tach sens., and pin 4 is the control pin. I supplied 12V to pin 2 and slowly increased the voltage to pin 4 up to 12V without frying the fan at all. This means that if you make a connector that is exactly the same as a 3 pin fan (a normal 3 pin to 4 pin molex adapter) and connect it to the PSU molex connector (these fans draw a lot of current so don't power it from the motherboard) and run two more wires to the tach and voltage wire from the motherboard to the tach and control pins of the fan, you would have control.

That being said, these fans run really fast at a full 12V and even down to 5-6V and are very loud. That's where the ULNA adapter comes in. These are simply just a 3 pin extension with a resistor inline on the power wire. There are two adapters that came with the fan and one is 150 ohm, the other is 50 ohm. These will reduce the 12V output of the motherboard header to about 5-6V or 3-4V depending on the adapter. This is a much more reasonable speed.

Electricguy skrev:En sån där nyare powermac? Dom har rätt snyggt chassie!