PSU trips with 7V fans

Danfoss2011

Danfoss2011

Danfoss2011

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PSU works fine, nice and stable. Yet soon as i use my 7v molex to power some fans it stops. Everything is the right way around

Whats the limiting factors of 7v on a psu with this mod?
 
Interesting. The molex mod in question treats the 5V line as ground, so current leaves the 12V rail and enters the 5V one. Power supplies expect to supply current on all the rails, and not recieve any.

Most of them seem to shrug off the unusual case, but there are theories knocking about that it decreases their lifespan. Your post supports this theory.

More usefully, go for 6V instead. 12V -> fan 1 -> fan 2 -> ground, the fans in series. As long as you have two similar fans they'll take about half the voltage each. The power supply will be quite happy with this. If you have an odd number of fans, you either go for an intricate arrangement of fans or run one of them through a resistor in fan controller fashion.
 
The fan are mounted to the shroud which is on the rad.

One side all the reds are tiwsted togther, the other all the blacks.

The single 12v 10A rated cable is then twisted on to the color coded corisponding fan cables, soldered togther and then heatshrinked.

No at modualr PSU, fixed cable.
 
I heard you can't power too many fans using the 7v trick. Maybe 8 is a bit too many.

Get yourself a fan controller or drop the voltage using some other means.
 
Tealc said:
I heard you can't power too many fans using the 7v trick. Maybe 8 is a bit too many.

Get yourself a fan controller or drop the voltage using some other means.
Click to expand...

Fan controler doesn't work. I wanted a single dia to control them all. The fans draw too much for most controlers. I did have the Lamptron FC8 which did the job but i had to import it from Japan but ive sold it now. However i just want one simple single dial
 
What about patching some diodes into the power entering the fans, a Diode will generally drop the voltage by about 0.8v-1.0v. Bung about 5 or 6 of them in series and you've got your 7volts. There's plenty of diodes available with large current ratings.

You can wire them to a switch, maybe even a rotary switch to change voltage as desired. The waste voltage will be dumped as heat.
 
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