Silencing the BEAST!

Well, I have just recently acquired a Delta Screamer FFB1212EHE thanks to Papercut & AAY(my NEW FAVORITE 120mm fan - 190CFM baby!)

I don't mind the noise (drives AAY up the wall though) having lived 4 months with a 80mm Tornado at full speed 24/7 before.

But since I love listening to music a lot more now (*cough* Z680 *cough* XFi *cough*) the fan screaming out its 59dB at sometimes is prolly a no no. Also the air whooshing through the radiator tends to get annoying (190cfm through a shroud and radiator.. :\ )

So the first thing I looked for was some rheostats. Unfortunately due to the insane power requirements, the capable rheostats costs more than the fan (try finding one that can handle 50w, 3.0A - Ohmites cost a bomb!) So I figured out that I could prolly use the 5v rail. It was a no go since the fan operates between 7v-13v.

So what did I do? I modded a pair of male and female molex connectors and to make it run 7v...

First thing I did was sacrificed a pair of male and female 4 pin molex connectors. I extracted the Molex connectors with my pin extractor and cut off the wires that would lead to the three pin fan header (in my case the header already fell off so no biggie there.)

After that I removed all the wires except the yellow wire (5v wire) and then I put a black wire as the negative (beside the yellow wire on the male connector) and the other end at where the red wire (12v wire) would be (on the female connector.)

Before hooking anything up, I checked the voltages using my multimeter to make sure its 7v.

After that my Delta is running dead silent (to me that is.) It's quieter than the panaflo high speed I was using before this.

So to make the fan quiet, I disconnect it and put this 7v molex thing and connect the fan back, to unleash the beast I just remove this thing and it will continue to churn out 190CFM. I was worried that the Delta would have motor noise (tick sounds) at 7v but I was relieved that there was none of it.

Sure it isn't as easy or convenient as a $$$ rheostat but hey, can't beat free can I?

Also as a safety precaution, I'm gonna use masking tape to make a flag for this thing so I don't go connect other stuff to it (I would not wanna imagine what would happen then.... )

Pic below, the 7v one is below where as the normal unmodded Molex connectors are above. You can also see the wires I cut off from the yellow and red wires.

 

Making your own rheobus is neither expensive nor complicated.
The heatsink for the power transistor is probably the most expensive part of it, if you have to buy one.

(See attached circuit diagram.)

/Olle

 

http://www.sidewindercomputers.com/si50warh.html

but the price is crazy

 

Yup, I would need to find a rheostat that is like the one powerslide posted.

Funny thing is I thought they marked up the price on those, but when I looked around, the cheapest 50w ohmite I found was 20ish USD....

 

Check my diagram! There's a definite difference between a rheostat and a rheobus.
To make a rheobus you don't need a rheostat, just a simple potentiometer that can handle a couple of milliamps, less than 1/1000 of what the fan needs.

The current through the potentiometer is first amplified a few hundred times in the darlington transistor, and that output is then amplified some fifty times more in the power transistor.
The high current runs through the power transistor only.

/Olle