I built my rheobus using 5W 100Ohm rheostats from here , and its been together and running all of my fans for the past week with ease, but today the rheo that was controlling my cpu fan changed from its normal way of reacting: normally i could run the fan with knob turned to lowest setting and register fan at around 3000rpm, and at max, around 7900rpm... today it only works if knob is at maximum, shuts off if knobs is any lower... fan is rated for 1.8W.... anyone got any idea what the hell could be wrong?
Check the rheostat with a multimeter for open circuit, symptoms spell a break near the max end. Working back, a 100R 5W should stand 223mA (I^2*R=W) even without any safety factors, you're only pushing 150mA max so it should have been fine. Note rheostats can only run at their rating if kept fairly cool. Go solid state - you know it makes sense.
Sounds like the pot is gone, probably the first turn on the resistive element burnt out. You could use the other , unused end instead. Of course the pot will work backwards then It does beg the question - why did it burn out? Possibly you are overloading it.
so just switch where the +v is soldered to one i dismantle it to make it better (a modder's work is never done.... might add some heatsinks while i'm at it to keep them cool)
macro was right... switching to the other one and it works its now 100x nicer looking because 90% of the wiring is on a PCB.... so neat....
