Proprietary Fan Blows, Gets PWM Upgrade

Proprietary components are the bane of anyone who dares to try and repair their own hardware. Nonstandard sizes, lack of labeling or documentation, and unavailable spare parts are all par for the course. [Jason] was unlucky enough to have an older Dell computer with a broken, and proprietary, cooling fan on it and had to make some interesting modifications to replace it.

The original fan had three wires and was controlled thermostatically, meaning that a small thermistor would speed up the the fan as the temperature increased. Of course, the standard way of controlling CPU fans these days is with PWM, so he built a circuit which essentially converts the PWM signal from the motherboard into a phantom thermistor. It’s even more impressive that it was able to be done with little more than a MOSFET and a Zener diode.

Unfortunately, there was a catch. The circuit only works one way, meaning the fan speed doesn’t get reported to the motherboard and the operating system thinks the fan has failed. But [Jason] simply disabled the warning and washed his hands of that problem. If you don’t want to use a CPU fan at all, you can always just dunk your entire computer in mineral oil.

13 thoughts on “Proprietary Fan Blows, Gets PWM Upgrade

    1. It’s a worry that the person writing this HAD article doesn’t seem to have read, or maybe didn’t understand, the article it refers to… Maybe they should read it (again?) and rewrite this article..

  1. I haven’t tried it myself, but I suspect if he would have just tied the power, ground, and tach lines of the Dell fan into the appropriate pins on the connector for his original one it would have worked fine. Just wouldn’t have PWM control but with the built-in thermistor control wouldn’t be as needed.

    Also the Dell fan really isn’t proprietary except for a non-standard connector.

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