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Replacing 780t front fans


Gamer_Gamer

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The fan control hub on the front of the 780 is DC system where you change speed by altering the voltage from 5-12v. The ML fan series are all PWM motors that generally require a constant 12v at all times and change speed through signal pulses. Now, some PWM fans can be controlled by altering voltage without damage to the motor. Sometimes this is revealed in voltage operating range in the specifications. We don't have any such clue on the ML series and you should assume it needs 12v at all times until someone can authoritatively tell you otherwise.

 

Regardless, there is another issue that may make this unappetizing. The control knob does 5, 7, and 12v in those increments. There is a mathematical disadvantage to using a large RPM band (2000 rpm) fan with a 3 step control knob. I think you know you don't want 3x2400rpm at the front on setting 3 (12v). The 7v setting is going to quite loud as well. That leaves step 1 as the only satisfactory setting. You would be better off controlling these fans from the motherboard or selecting something else.

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In theory, you could put all three on one MB header. Most have a 1.0A limit and 3 ML120s would be 0.90A (0.299 each). However, a limit is a limit --- don't break it. The current rating for a fan is an average current over time. That can create a problem. It's not your normal use that creates a danger. It's the 100% fan test on start-up, reboots, etc. where your "average" might exceede the limit. If possible, put 2 on 1 header and one on another. That would be give you lots of headroom and it's also the way I run 3x120 in the front for the reasons above.
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