Review: Sunbeam Rheobus Fan Controller

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Simple Fixes for the Bright LEDs

The photo above shows LED details. Their pins actually plug into sockets on the PCB, and are removable. Just press on the bulb from the front and it comes off the little plastic holder in the front panel. The top photo shows the LED removed next to the IDE power plug. If you are electronically savvy, you could replace these LEDs with ones that are not so bright. Or just remove the LEDs altogether, as the controller works fine without them.

You could also do what I did in the photo above: Pull the LED head out of the front panel hole and position it so that its lens is pointing at the inside of the front panel. That's how the second photo at the beginning of this review showing the more subdued lights was taken. To me, it is much more livable than leaving the LEDs in stock form.

What about Voltage Control!?

Each of the four channels was tried with several different 12VDC fans: Two 80mm Panaflo variants, a high speed 80mm Sanyo-Denki, and a 120mm Antec. All the controls worked and measured very closely to each other. There was no humming or buzzing coming from the controller at any control setting or combination of control settings. No extraneous noises of this kind from any of the fans could be attributed to the controller, either.

As mentioned earlier, each knob actually operates a switch. The off position is at about the 7:30 position. When it is rotated clockwise, it turns on, and the LED for that channel turns on at full brightness, in red. The minimum voltage is 0.2V. No 12V fan will spin at this voltage. At the 12 o'clock position, voltage output remains at just 2V. At 1 o'clock, output is 4V. Between the 1 and 2 o'clock positions is where most 12V fans begin to spin -- about 4~6V. Around the 2:30 mark, 7V is reached. This is when the LED turns blue. After this point, voltage rise fairly quickly to a maximum of 11.5V at close to the 6 o'clock mark.

Knob position
Voltage Output

The fan voltage control knobs really have a useful range of only about 1/3 of a turn, from 1:30~5:30. The rest of the knob's rotary range is basically useless, as fans don't get enough voltage to even turn on.


The Sunbeam Rheostat has some very positive qualities:

  1. Amazingly low price from the sample supplier SVC: The manufacturer's suggested retail is $30 but SVC sells it for just $18. That's cheaper per channel than even a Zalman Fanmate 1.
  2. Full voltage range from 0-11.5V can be seen as a good thing for hardcore tweakers. Some 12V fan actually start at even 4V or less so the extra range could be useful in getting some fans to run really slowly.
  3. A mere 0.5V loss at full output suggests efficient circuit design and implementation, and the robust 20W per channel rating is an added bonus for running a large complex system with many fans at low speed.
  4. It makes no noise whatsoever nor cause any extraneous noise in fans at any speeds or combination of settings.
  5. The front panel is not that bad for an $18 item -- aside from the over-bright LED (which can be easily fixed) and somewhat cheesy blue graphics and lettering,

It does have some points against it, too:

  1. More than half the control knobs' range is useless, so it can be very touchy to set within the limited useful range.
  2. There is no scale around the knobs to help a user visually mark positions for repeatability of settings. This would have been a very simple thing to implement. One could use a felt pen, or some other marker, I suppose.
  3. When an LED is on, it does not mean that the fan is running. The LEDs are turned on or off simply by the setting of each knob, not by whether a fan is running or connected. This, in combination with the low voltage capability, is potentially dangerous. For example:

    A control is set so that a fan start up and runs very quietly, at ~6V. The control is accidentally touched and the fan stops running. Because of the low noise level, this change is not noticed -- the LED remains on. The user moves away from the computer for a while. Some kind of thermal overload occurs as a result of the stopped fan. The user comes back and begins screaming when he/she realizes the system has been cooked.

One way around this potential problem is to use the controller in the range where the LED turns blue, which is ~7V or higher. When the LED is red, it then becomes immediately noticeable. This is not a bad solution, but not ideal for many people who like to ramp their fans down as low as 5V.


The Sunbeam Rheostat is very good value for a fundamentally sound, high power 4-channel fan controller. Because of the potential to turn fans off without the user being aware, it is not ideal for casual users. Rather, it is more suitable for more obsessive types who will be vigilant about fan settings. I can also see electronically savvy folks using the Sunbeam as the basis for modding or creating their own customized fan controller. Recommended with caution.

Our thanks to Silicon Valley Compucycle for the Sunbeam Rheostat review sample and their kind support.

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Look for the Zalman ZM-MFC1 Multi Fan Speed Controller

review soon in this section.

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