problem FIXED!
no need for a resistor! just one 1uF capacitor from PWM control pin to GND pin! when i said that i tried few capacitors but they did nothing... i was connecting them from +12V to GND because i couldn't imagineeeeeeeeeeeeeeee!!!!!!!!!!!!!!!!!!!!!
something i've noticed and i don't know if it is ok or not... is that when i'm using the 1uF capacitor and i have the BIOS function at "ultra Silent" the RPMs of the fan are getting lower than without the capacitor.
so now... i know two things!!! first the PWM is full of ripple noise because of the reason
MrAl gave (?) and second that the motherboard probably has missing components or that is kinda faulty (?)
if it is faulty i think i should RMA it...but how am i going to explain that to the dealer store?
Hi again Whiz,
That's great to hear, but the solution isnt that great to hear.
The reason i say this is because there was no series resistor included
in the 'fix'. The series resistor was supposed to be there for at least
two reasons:
1. To help the cap work better in filtering
2. To protect the Mother Boards drive circuit from high peak currents
Now we can do without #1 above, but without #2 we risk doing
long term damage to the MB, which would be hard if not impossible to
fix later on.
Solution? Simply add a series resistor. Even 100 ohms is better than
nothing, and this could allow a smaller cap value too.
I'd start with 1k and then cap values:
0.01uf, 0.1uf, and 1uf (now that we know 1uf works without R).
If that doesnt work, then 200 ohms and those same cap values,
starting with the lowest value and working toward the highest.
If that doesnt work, 100 ohms and same cap values, etc.
I'd hate to see something happen to the MB so the fan doesnt
work at all anymore, or worse.
The idea is to use the highest value resistor that will work and the
lowest value cap what will work. This is best for both the fan and
the MB alike.
Good luck with it...