Nexus NX-9003 350W Hybrid PSU

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Nexus' tagline for the NX-9003 is SFB: "Security Fan Backup". Nexus has gone to some trouble to make sure that people know that the fan is not supposed to spin under ordinary conditions. The diagram below, from Nexus' web site, is supposed to show how it works.

The basic idea is clear enough. Neither fan will start until a thermal threshold is reached. Once the fans turn on, they remain at a constant speed until the next threshold is reached, when the fan speed jumps up to a faster speed.

There are two fan controllers: One for the fan in the power supply, and another for two external fan headers. Each controller has its own thermal sensor. Both fan controllers are integrated into a PCB separate from the main power supply. In addition to the usual mess of wires and fan headers, there is also a buzzer that will produce an audible warning if either of the two sensors gets too hot.

The fan controller has its own PCB, right next to the fan itself.

The thermal sensor for the main cooling fan is on the smaller of the two heatsinks.

The thermal sensor for external fans is on an external lead, and can be placed wherever the user sees fit. For our testing, we placed the sensor right next to a sensor of our own so we could track its temperature / voltage relationship.

On top: Our own thermal sensor. The green thermistor below it controls the external fan headers.

A high speed Yate Loon with sleeve bearings.

The fan is an orange Yate Loon, model D12SH-12. This is a higher speed version of the Nexus Real Silent 120mm fan. It's rated for about double the airflow. Unfortunately, this is not a good sign: A faster fan is almost always noisier.


The following cables come with the NX-9003. All cables are sleeved in black mesh except for the fan headers and thermistor, which are sleeved in heatshrink material. The IDE drive connectors have grips on them to ease removal.

  • 19" cable for main 20+4-pin ATX connector
  • 19" cable for auxiliary 4-pin 12V AUX connector
  • 19" cable for 6-pin PCIe connector
  • 31" cable with three SATA drive connectors
  • 31" cable with two 4-pin IDE drive connectors and one floppy connector
  • 31" cable with three 4-pin IDE drive connectors
  • 2 x 20" orange cable with one 3-pin fan header
  • 13" cable with the thermistor that controls the two fan headers.

The orange cables are fan headers.

The assortment of cables is extensive enough for most systems, and none of them are particularly long or short. Only a single PCIe cable is included, as befits the unit's relatively modest output rating.

The fan headers are a little on the short side. In a standard ATX case, this shouldn't be a problem, since most of the system fans are right next to the power supply, but it would be hard to reach a front-mounted fan.

The length of the cable for the thermal sensor may be more of a concern. At a puny 13", its range of positions is limited.

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