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I got this crossfader out of an old DJ mixer. I want to use it in an electronics project of my own design.

It's got 4 pins - which I presume are 2 x input, 1 x output and 1 x ground.

Using my Fluke 179 multimeter, how do I figure out which pins are which, specifically which is the ground pin?

Thanks in advance,

Ryan

Multimeter and crossfader

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  • \$\begingroup\$ You will have to examine the PCB itself. It is not possible using the DMM only. \$\endgroup\$ – Eugene Sh. Jan 9 '17 at 17:12
  • \$\begingroup\$ What desk does that come from? Is it mono? Are you sure that there are only 4 pins? A stereo desk would have 6 pins on all the faders - 3 per channel. \$\endgroup\$ – F. Bloggs Jan 9 '17 at 18:40
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The crossfader is a variable resistor, so you need to find which pins are the ends (inputs) and which pin is the wiper (output). The biggest resistance will be between the two inputs, and this won't change as you move the slider. The resistance between an input and the output will vary as you move the slider, and each input's resistance will move in opposite directions.

Your part looks like a Behringer CFM-2, but I couldn't find a datasheet.

Based on your comments, here's my proposed pinout:

schematic

simulate this circuit – Schematic created using CircuitLab

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  • \$\begingroup\$ Right, so actually there are two inputs and two outputs? And one of the outputs is used as a ground? \$\endgroup\$ – Ryan Ashton Jan 10 '17 at 3:31
  • \$\begingroup\$ I haven't seen the part, so I could be wrong, but I believe the ground is just used for shielding and isn't really an input or output. Did the multimeter readings work out? \$\endgroup\$ – Ken Shirriff Jan 10 '17 at 5:36
  • \$\begingroup\$ Yeah - it seemed to work. Pins 1 & 2 showed variable resistance from 1 ohm to 50 k ohms when the slider was moved, as did pins 3 & 4. But then pins 1 & 3 also showed this variable resistance and so did pins 2 & 4. Pins 1 & 4 showed the same resistance (50 k ohms) no matter where the slider was and would pins 2 & 3 when connected - though sometimes with pins 1 & 4 and 2 & 3, the meter would go into the m ohms range or overload. So what does that tell you about the crossfader? \$\endgroup\$ – Ryan Ashton Jan 10 '17 at 12:59
  • \$\begingroup\$ Is the resistance between pins 2 and 3 zero ohms? If so, then pins 1 and 4 are the ends of your variable resistor and pins 2 and 3 are both the wiper. I drew a diagram above. (The m ohms reading was probably just bad contact between the DMM probe and the pin.) \$\endgroup\$ – Ken Shirriff Jan 10 '17 at 18:48

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