Max Baker wrote: > Phil, > > I will "see" your motherboard pictures and "raise" you a schematic :) > > http://warped.org/linux/j7f4r30fan.pdf > > The fine, fine folks at Jetway were nice enough to send me an actual > schematic for the J7F4 board -- well only the page w/ the fans on it. > They get an A+ for customer/Linux support, buy their products. Absolutely! I agree with your analysis, but note that the control components are all marked "NC", which I imagine means "not connected", while the 0-ohm link is not marked "NC". > C3) Bypass cap for the power supply node of the fan? This is odd; the Fintek datasheet shows a capacitor in this position, but doesn't give a value. Putting a largish capacitor here (this is 10 uF I think) will rather screw up the PWM control in exactly the way that Jean and I have been discussing, i.e. even if the "on" period is quite short it will be enough to charge the capacitor for the whole cycle. Having experimented I have not added a capacitor in that position on my hack. They may be imagining that it has the effect of "smoothing" the PWM signal (e.g. 50% 12v smoothed to 6v). To make this work you would need an inductor and a diode and you'd have built yourself a simple switch-mode supply. > If I have R3, then I > will not be pulling out the soldering iron and scope, but will be > returning the board and getting an EPIA board. Do you have any firm indication that the EPIA C7 board does have fan control? Phil.
