Silencing my signal generator

Waveform generator

My RIGOL DG1022Z waveform generator made a lot of noise when I first switched it on. There’s a little fan in there, operating on 12 Volts.

Having opened up the device, I took out the fan and tried to operate it on 9 Volts. That still worked adequately, and made significantly less noise.

Running on 9 Volts it draws around 50 mA, so the resistance is about 180 Ohms (9 / .050). The feed line from the circuit board carries 12 Volts. To bring the voltage for the fan down to 9 Volts and maintain the 50mA, I needed a total resistance of 240 Ohms (12 / 0.50). So I used a 56 Ohms transistor I had around put it in series with the fan; that reduced the sound neatly to an acceptable level.


case opened up
Case opened up, fan removed
56 Ohm resistor
Soldered a 56 Ohm resistor in the feeder wire
Wrapped it in shrink tube
Wrapped the resistor in shrink tube for isolation
Back in place
Mounted the fan back in place and connected it again