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Ablecom SP262-1A 260W 1U PSU

Information about slowing down the fan in an Ablecom SP262 PSU (so that it can be used in a non-machine room environment)

This PSU is supplied by Supermicro in a SC512F 1U chassis. The label is:

Ablecom SP262-1S 260W PSU (label)

The inside of the power supply shows a single exhaust fan (i.e. no fan on the left where the air in drawn in).

Ablecom SP262-1S PSU (inside PSU frame)

The fan is an AVC model DB04028B12H 40x40x28mm DC brushless fan. It has a two wire connection. There is no PWM speed control, or tachometer output.

Rated voltage: 12v

Operating voltage: 7.0 to 13.8v

Rated current: 0.38A

Rated input power: 4.56W

Speed: 11000RPM

Noise: 50dBA


AVC Model DB04028B12H Fan

The speed and the resulting noise are the issue that is attempting to be addressed. There is no temperature sensor to provide feedback to control the speed of the PSU fan. By reducing the 12volt DC supply to 7volts (with a 5.1volt zener diode) the fan noise is significantly reduced, but not eliminated.

To provide full speed control a 4pin PWM fan is used to replace the existing 2pin fan. The 12volt supply is drawn from the power supply header, the tachometer signal & the PWM control signal are extended to the motherboard. The fan used is an Everflow R12028BU, and has the following speed characteristics:

Everflow R124028BU 4pin PWM fan - PWM vs Speed

It is important to note that this solution doesn't incorporate any sensing of the internal PSU temperature. Care should be taken not to cause the PSU to overheat.


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