[mythtv-users] OT: EPIA 800 Fan is noisy

Matthew McClement mythtv at macker.co.uk
Thu Jun 28 10:48:48 UTC 2007

migmog wrote:
> On 27/06/07, Derek Conniffe <derek-mythtv at rivertower.ie> wrote:
>> I've taken to disconnecting (snipping) the + connector to the CPU fans and
>> connecting it to the red 5V wire on a spare hard disk connector - I'm sure
>> this is pretty bad but it makes the fans a lot quieter (they run slower
>> and the RPM, and CPU temp, can be read with lm_sensors).
>> Derek
> You don't need to do that. Just plug in the connector backwards, and
> you get 7V instead of 12V to the fan, and it slows down almost as
> much. The sensors all still work.

I don't see how that would work. To get 7V from a molex connector you 
need to use +12V for power and ground it with the +5V, both of which are 
on the edge. The two middle wires are both ground. Reversing the 
connector would just give you 5V.

For motherboard 2, 3 and 4 pin connectors you have GND, PWR, signal(3 
and 4 pin) and PWM control(4 pin). Reversing that would result in some 
truely odd conbinations(2 pin might decide to work, 3 pin you'd be using 
signal as ground and 4 pin you'd land up trying to power the fan using 
signal and PWM control).

But maybe I'm just missing something really obvious.

On a mildly related note, I recommend looking at Zalman fans. Most of 
the 80-120mm fans come packaged with a premade resistor cable that'll 
drop the voltage for the fan if you want to run it at a lower RPM 
without resorting to cabling shinanigans and/or you're too lazy to make 
your own. The resistor cables are usable with other fans as well, which 
is a nice bonus.


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