PSU modding help

No9 · Post by **No9** » Sat Oct 04, 2008 6:01 am

(note work is not done by me, thankfully I have an electrician in the family)
I have a coolermaster 500w Igreen that I wanted to do a fan replacement to a quieter fan. So I asked my brother to do the soldering work and replace it with a 120mm glacialtech Silentblade.

Now I just ran some the pc for the first time and I note that the fan needs a gentle push with a chopstick to get going. ie it tries to spin and gets stuck at about 1/4 of a revolution and then a gentle nudge is required. I can't figure out why? (The fan power was spliced onto the existing 2pin connector from the old fan). The fan was working fine and the I absolutely guarantee the soldering work to be top notch.

What is going on?

The coolermaster fan that was pulled out was chb12012db-O which bring me to a chinese website which I can't read. From what I can gather these are the specs

sizeï¼š120mm x 120mm x 25mm
Voltageï¼š12V
Input currentï¼š0.47A
input powerï¼š5.56W
rpmï¼š2600RPM
cfmï¼š94.3CFM
dbï¼š47dBA

The strange thing is that once it gets going it goes and goes and goes very smoothly and with consistenat and even RPM's. Which leads me to believe its a voltage issue with the fan

dukla2000 · Post by **dukla2000** » Sat Oct 04, 2008 7:33 am

There is no quick fix - the psu has fan control circuitry and it seems it starts at a low voltage, which is just too low to start your glacialtech. You could try another fan (and/or search this site for fan start voltages - there has been plenty of discussion). The psu fan control circuitry is 'poor' in that starting @ 12V and then dropping would be far preferable.

The other thing you could try is playing with a diode or capacitor in the circuit: I am no electronic engineer so am not sure how to get a boost/start voltage - look for posts here by cpemma and check out his website.

SebRad · Post by **SebRad** » Sat Oct 04, 2008 9:27 am

Hi, if you ever didn't start the fan I suspect the temp in the PSU would rise fairly quickly and thefore the V being fed to the fan would rise and likely quickly get to a point where the fan would start of it's own accord. The first PSU i mod'd was like this, the fan tended to start, just, under cold boot but if it didn't it soon started as the PSU temp rose and the voltage supplied by the fan controller increased.
In short, it should be OK!
Seb