Simple PS3 Fan Speed 555 Pulse Mod No Pots Options

[relaxxx]

I've been playing with my 555 pulse timers and figured I'd post what I've done so far as there really doesn't seem to be a decent schematic online anywhere.

I didn't want any potentiometers, I don't want the owners turning the fan down. Just a simple 555 timer schematic for running the fan at a decent rate.

Runs off the fans 12V Brown wire so no need to wire from another source. To regulate the pulse peek voltage to 3V I used a common LED and it also helps to visually gauge the pulse frequency.

With 4.7K ohm at R1 it is still quite fast and about as loud as a 360 12V Mod. Combining resistors to make around 5K ohms or so should quiet it down a bit more. You can change the C1 from 1uF to 10uF but then you must change the R1 value accordingly.

[ProCision]

Have you noticed any change in your method when the system is running 4.0 FW? I used to mod the fan by taking the 3.3v power supply source and cutting the gray wire and running 40k-150k ohms in line. That used to work great up until that last 3 ps3's I have fixed. It will start running the fan @ 50%(ish) and after 5-10 min. the fan will be barely running at all. So my method is out the window. Time to use your method.