Topic: Instructions for fader repair from Frontier Designs tech support:

I was just guided through a fader repair via email for my non-working Alphatrack.  Here is the content of the email that helped me solve this:
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Here are the instructions for repair:

First, unplug the AlphaTrack from your computer. You'll need a Torx screwdriver size T20 to take out the 4 screws in the back of the AlphaTrack . If you turn the AlphaTrack face down you'll see 3 holes and the 4th hole is under the rubber foot that is closest to the right encoder. Take out the 4 Torx screws using the T20 screwdriver and the bottom piece of the AlphaTrack should separate from the top piece. Now you should be able to see the fader . There are 3 pins on the bottom of the fader , 4 pins at the top of the fader and 2 on the fader 's motor. If you look at the faders 4pin side (top) you'll see a wire going from the two outermost pins. Likewise you'll see a similar wire connecting the two outermost wires on the 3pin side (bottom). Also, I should note that the two middle pins on the 4pin (top) side of the fader  SHOULD be soldered together.

The first thing I would check is that the two wiring harnesses connected to the fader are well seated. I've seen a few that had intermittent fader issues all because the 4 pin wiring harness wasn't fully seated.

If the harnesses look ok then the next thing to do is to inspect the wires of the fader. It's possible that one of these wires/pins just needs to be reflowed with a soldering iron. If you look closely you might be able to tell if there's a poorly soldered wire. I'd reflow all the wires just to make sure. Be careful resoldering the motor wires making sure that you only solder to the motor pins and make sure none of the solder or wires are touching any of the metal part of the motor casing (both the metal between the two motor pins and the metal on the motors shell as this will create a short). What I would do is reflow all the other wires and then test the AlphaTrack and if it still doesn't work then carefully reflow the motor's wires.