OC & Modding Need help with replacing UPS fan

A

aniket.cain

Disciple
I have an APC 1600VA UPS (BVX1600LI), which has enough power for my PC but has a very annoying problem.

It has a very loud fan which kicks in if the load is above ~250 watts, which means it is always on when I have to play any games on the PC. It is simply intolerable for me. I wanted to replace the fan with something quieter.

This is the information that I have gathered so far about this fan:
  • The fan model is DA06025S12MF (Yimeng brand apparently).
  • There are 3 cables on a JST XH connector - red, yellow, and black.
  • When the fan is running, the voltage b/w Red and black is 11.96V (it is a 12V fan), and the voltage between Yellow and black is 2.64V.
  • If I stop the fan manually, the voltage between the Yellow and black is 4.98V. This looks a locked rotor signal.
Any idea how can I replace with something else, say Noctua NF-A6x25 fan?
 
Get another quieter fan of the same length and breadth, that is 60mm x 60mm; the height is not that important. Open up your UPS's body and remove the existing fan, retaining the screws. Use the screws to install the quieter fan in its place. Beware, there are high voltages inside the body of the UPS, so ask a professional technician if you lack experience in this field.
 
Unfortunately it is not as simple as replacing a PC fan. Normal 3 pin fans send a tach signal on the 3rd wire, while the fan in this UPS uses it to detect a locked rotor.
 
aniket.cain said:
Unfortunately it is not as simple as replacing a PC fan. Normal 3 pin fans send a tach signal on the 3rd wire, while the fan in this UPS uses it to detect a locked rotor.
Click to expand...
Did you try to run a fan with just 12V, I mean no third wire? If the UPS doesn't complain about the absence of rotor signal, then you should be good. If it does need a signal, (all it would need is a voltage) use very high resisters in ratio and solder them between Ground and 12 v to get the desired drop on the third pin. Since the resister value would be very very high, current would be almost zero, so no damage to any components. However, I do think that the fan will work with just two wires.
 
dvader said:
Did you try to run a fan with just 12V, I mean no third wire? If the UPS doesn't complain about the absence of rotor signal, then you should be good. If it does need a signal, (all it would need is a voltage) use very high resisters in ratio to get the desired voltage and solder on between Ground and 12 v to get the desired drop on the third pin. Since the resister value would be very very high, current would be almost zero, so no damage to any components. However, I do think that the fan will work with just two wires.
Click to expand...
Thanks. I tried it with only 2 wires, but it does not work with just 2 wires or without the fan connected. It shuts down immediately when load goes above 250W.

I too was thinking of using resistors or a buck converter to send back the required voltage to yellow (2.64V).
 
aniket.cain said:
Thanks. I tried it with only 2 wires, but it does not work with just 2 wires or without the fan connected. It shuts down immediately when load goes above 250W.

I too was thinking of using resistors or a buck converter to send back the required voltage to yellow (2.64V).
Click to expand...

Hey can you try connection the third pin as is. The UPS might be using an off the shelf fan and converting the tach signal internally to get rotor sense. Let me know if you havent tried that yet.

Also a buck converter would be a lot of work to fit in. Use a 400k and a 100k resister in series and the drop around 100k would be about 2.4V. Total current (12/500000 A = 24 uA) amounts to nothing.
 
dvader said:
Hey can you try connection the third pin as is. The UPS might be using an off the shelf fan and converting the tach signal internally to get rotor sense. Let me know if you havent tried that yet.

Also a buck converter would be a lot of work to fit in. Use a 400k and a 100k resister in series and the drop around 100k would be about 2.4V. Total current (12/500000 A = 24 uA) amounts to nothing.
Click to expand...
Thanks for the inputs. I have ordered a few required parts from robu. I will update over the weekend if I make some progress.
 
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