Alesis Micron Control Knob Encoder Replacement

a.k.a. How to void your warranty and potentially destroy your Micron at the same time.

Every photo on this page may be clicked to reveal a larger image.

Comparison of the Original and Bourns Encoders

Bourns manufactures an encoder by the part number of PEC11-4220F-S0024 which is similar enough to the control knob encoder of the Alesis Micron to serve as a replacement.

On the left is a replacement encoder which I obtained from Alesis for $4.00 USD. You'll have to email their support, who after several days will forward your email to someone who can help you, who will then ask that you send your credit card details via unencrypted emails. I suggest inquiring about paying with a money order.

On the right is the Bourns encoder which I obtained from Newark for $1.09. Links to order this component are at the bottom of this page.

In the center is one U.S. penny, for size comparison.

Outside of the U.S., it seems the standard item for size comparison is a ruler, so here are the encoders next to a nice little PDF Printable Ruler.

(two more photos showing side dimensions)

When encoders are sold, they're usually described like "20 mm Rotary Encoder w/ Push Button" or some such.

This is a photo of the measured dimension. This dimension is cited because it is assumed that you will bolt the encoder to a surface using a nut and the threaded area of the encoder.

As you can see here, the encoder in the Micron is a 19 mm encoder.

The Bourns replacement is described as a 20 mm encoder, but as you can see here, it is actually 21 mm.

In the Micron, however, the encoder is not bolted to the panel and so another important dimension is from the bottom of the plastic, which rests on the circuit board to the top of the main body of the encoder.

This dimension is 6 mm on the original encoder.

On the Bourns encoder, this dimension is 7 mm. In total, this makes the Bourns encoder 3 mm longer than the original encoder.

(I realize it appears to be 6 mm in the photo, but I'm holding a ruler to one right now and it is indeed 7 mm.)

This is a photo of the encoder from Alesis disassembled. The top left piece is the push button. The top right piece contains wipers which connect with the bottom left piece (when flipped over), to form the rotary sensor.

The detent action is created by a steel spring against the side of the white plastic wheel. The steel spring is difficult to see in this photo. It is at the top of the piece. It is a flat piece of steel wire bent in the center to form a point which contacts the white plastic wheel.

I believe my original encoder failed because this mechanism was too abrasive on the plastic. When I disassembled it, it contained a white cream-like substance which I assume was what was preventing proper operation of the rotary sensor, as nothing else appeared to be wrong with it, aside from the detent action being virtually non-existant.

This is a photo of the Bourns encoder disassembled. The top left piece is the push button. The top right piece contains a pattern which connects with the wipers on the bottom left piece (when flipped over), to form the rotary sensor.

The detent action is created by a copper alloy spring against the top of the black plastic wheel, which has a series of ridges.

I believe this detent action is less likely to result in failure of the rotary sensor for the following reasons:

  • The copper alloy spring applies less force than the steel spring of the encoder from Alesis, which should translate to less wear on the plastic wheel and less debris.
  • The area where this occurs is more separated from the area where the rotary sensor functions. There is a ridge around the rim of the black plastic wheel which sort of forms a bowl which may help to contain any debris away from the rotary sensing mechanism.
  • The copper alloy spring is well lubricated. The steel spring in the encoder from Alesis does not appear to be lubricated at all.
For these reasons, I recommend the use of this part in place of the original part from Alesis.

The Replacement Process

Replacing this encoder is not an easy task. For someone wishing to repair their Micron themselves, it will be easier to replace the entire circuit board that the encoder is attached to rather than attempt to replace just the encoder. However, if you're going to replace the circuit board anyway, there's little reason not to attempt to replace just the encoder first. Unless you seriously mess up, the worst you'll do is ruin the board and have to replace it, which you were planning to do anyway. So all you have to lose is whatever you pay for the new replacement encoder. Also, when you replace just the encoder, you have the option to replace it with the Bourns encoder which appears to be more durable. If you order the entire circuit board from Alesis, it will come with the same encoder you had before.

On the other hand, if your control knob still somewhat works, or if your Micron is still under warranty, you may want to talk to Alesis and determine the cost of the circuit board so that you know how much risk you are taking.

Important: At all steps in this process, no excessive force or heat should be required. If you find otherwise, you should pause to contemplate what the problem might be. This is a difficult task, but not difficult in that you may not be strong enough or you may not have a hot enough soldering iron. It's difficult in that it is easy to damage more than you repair. The best weapon against this type of difficulty is time and thought, not brute force. Use caution!

To begin, first remove the control knob from the Micron and set it aside. To remove it, simply pull on it. It will come off.

Then unscrew the plastic rings around the connectors on the back of the Micron. Set these aside somewhere where they will not get lost.

Then remove all of the screws from the bottom of the Micron. Take note of the fact that there are two different sizes of black screws. I believe the short ones belong along the back panel, or at least that's where I put them after realizing I had two sizes of black screws and no idea where the short ones go.

Make sure you've put these things where they will not become lost.

I like to keep my screws attached to a magnet. It's much harder for them to roll away when they're stuck to a magnet. If you don't have a magnet, try a bowl.

After removing the screws, carefully (keeping in mind that nothing is holding your Micron together anymore) flip the Micron right side up.

Then tilt the keyboard upwards as pictured, and partially pull it out.

Then set the keyboard down as pictured. This will allow you to flip open the case while leaving the keyboard inside, which is necessary as the cable to the keyboard isn't very long.

This is about the only way you can arrange things with the Micron disassembled. The cables aren't long enough to arrange things more conveniently, and unfortunately, the cables are glued in place. I imagine they could be removed anyway, but I didn't feel like messing with them.

After removing the three screws holding the small board with the encoder on it, it can be removed and moved slightly away from everything else.

To remove the encoder, begin by using clippers to cut the leads to the encoder as close to the encoder as possible. The lead nearest the cable on the board is difficult to get to. I suggest clipping the others, then bending the encoder back and forth until this lead breaks.

With the old encoder out of the way, remove the pins by grasping them with pliers on the component side of the circuit board (pictured above) and pulling them out while heating the solder on the solder side of the board (pictured at left) with a soldering iron. If done correctly, the pins should come out with very little force and less than two seconds of heat from a 30 watt iron. If this doesn't work, pause to carefully look at everything that might be causing a problem. You do not want to accidentally damage the board, so use caution.

Some of the pins will not have a large enough surface to grasp with pliers. For these, you'll have to remove some solder first. Do not do as I did and attempt to pull the pins out backwards just because they're easier to grasp on the solder side of the board. The side which was clipped may not want to fit through the hole. Mine didn't, and I pulled up a trace in the process, which is a very bad thing to do. Had I taken my own advice and not tried to force the pin through the hole, but instead paused to wonder why it wasn't coming out easily, my board wouldn't be damaged.

To remove solder, you'll need a solder wick. I make mine out of stranded wire, as real solder wick is a little too expensive. I like to use old appliance cord or speaker wire. Strip off a few centimeters of the insulation, twist the strands together, then slightly untwist them so that it isn't a tight twist, but the strands are still held together. Then cover the wire with a soldering paste or flux.

Do not use pipe soldering paste. Electrical soldering paste is designed for electrical soldering, and is safe for the electronics. Pipe solder is designed to be non-toxic (or so we hope), dissolvable in water, and good for pluming, but it will corrode your electronics like mad. Find a real electronics soldering paste or flux. Also, do not attempt to do this without soldering paste or flux. Doing so requires a lot more heat and force, as the copper will oxidize immediately when heated, and oxidized copper doesn't solder well. Solder paste or flux will remove oxidization and coat the copper to prevent new oxidization from forming. It will also make your circuit board dirty, but it's harmless. It's designed not to be electrically conductive, which is another reason to not use pipe solder paste.

Once you have prepared the solder wick, place it on the solder to be removed, and heat with the iron. To help the process, lightly press the iron through the wick into the solder, and twist the wick back and forth to help the solder flow into it. When the wick is full, make a new one.

Be cautious not to overheat the circuit board. While nothing strictly bad happens, and while there is no clear threshold of overheated-ness, it's still a bad thing to do. The goal in soldering is always to heat things as little as possible. Heat will stress the board and possibly damage components.

Also try not to use too much force. This can damage the traces, the green solder mask, or the through-hole, a small copper tube which runs from one side of the board to the other, through which the pins are placed.

Once excess solder is removed, you can hopefully use the soldering iron to push the shorter pins so that they extend out of the component side of the circuit board, where they can be grasped with pliers and removed.

Once all of the pins are removed, use the solder wick again to remove as much of the solder as possible from the holes. You can make smaller wicks which fit into the holes to remove as much solder as possible. You need to remove virtually all of the solder, otherwise the pins of the new encoder will not fit into the holes.

Again, be cautious. If it isn't fairly easy to do, you need to pause and consider what you may be doing incorrectly. Otherwise you may damage the board.

The next step is to insert the new encoder.

Important: The two large pins on the Bourns encoder are too large to fit in the holes on the circuit board. I originally recommended bending the pins flat as shown in the photo, but after a month of use, the encoder basically fell apart, a result of the fact that part of the function of these pins is to hold it together. I now recommend straigtening the pins, then bending them under the encoder, so that they help to hold the pieces of the encoder together. I've since used the encoder for 18 months and it still works, so this is clearly a better solution.

Note that it is generally a bad idea to drill into multi-layer circuit boards, as you never know what you'll cut in to between the layers, and so I do not recommend making the holes larger.

The remaining pins should fit easily into the board. If they do not, then again, pause and look at the problem. You may still have too much solder in the holes. The pins may be bent and not aligning with the holes in the board. If you force it, the pins on the encoder may bend or break, and then you need another one.

Finally, it's time to fix the problem you created when you accidentally pulled up that trace. Don't you wish you'd listened to me when I said to be careful and pause to think when things seem to require force? I sure wish I had.

You'll want kynar wire, which is sold as "wrapping wire" and is used with a special wrapping tool, which hopefully contains a nice little wire stripper in its handle. This wire is very thin and flexible enough that it is ideal for correcting these sorts of accidents.

Rather than attempt to solder to a via (which is a tiny hole in the circuit board where the trace simply goes from one side to the other) I recommend following the trace until it leads to a component pin, and soldering to that, which is what I did in this photo.

Finally, reassemble the Micron. Be certain not to include any loose bits of metal within the Micron which may potentially short something out. Take note to replace the short black screws into the same holes which they came out of. Do not forget the plastic rings on the back.

Using the Bourns encoder, the control knob now sits 3 mm higher than before, which looks somewhat strange, but it works.

The Bourns replacement also comes with a small washer and nut. I do not recommend their use, as the original design of the Micron wasn't intended for them and using them may bend the circuit board to which the encoder is attached or place stress on the encoder which pulls it apart over time.

The Conclusion

Once the Micron is reassembled, the encoder should work perfectly. At least mine does, and I hope yours will as well. The detent force isn't as great as with the original part, but as I mentioned above, I believe this will help to lead to a longer component lifetime. The push button action of the knob feels better because it moves downward slightly more and has much more of a click to it. Also, even when new, the original encoder seemed to occasionally miss a click when I went from moving in one direction to moving in the other direction, but the Bourns encoder doesn't seem to have this problem.

I have every reason to suspect that this encoder will perform better than the original part, but ultimately, only time will tell.


It's been over two years (IIRC), since I replaced the encoder in my Alesis Micron and it still works! That's much better than the few days I got out of the encoder that came with it. Granted, after a month or so with the new encoder I decided that the Micron is a total piece of shit and so I haven't used it much since then, but I'm sure that if I had replaced it with the original part, it would have broken again by now, and so I consider the Bourns encoder a success. Hell, it has out-lasted the pitch wheel, and I don't even use the pitch wheel.

Where to Order the Encoder

Someone emailed me to let me know that Newark no longer sells the encoder I purchased.

I've found that Digikey continues to sell it, though they're out of stock at the present moment. They claim they'll have more in 28 days just as soon as someone orders one, as they're apparently not planning to order more until then. Given the popularity of this web page, I expect that now that I've linked to them, they'll have more within a month or two and they'll never let them run out of stock again as people will be constantly ordering them.

PEC11R-4220F-S0024, the 20 mm version described and photographed above.

Digikey also has two other versions of the same encoder, with different shaft lengths.

PEC11R-4215F-S0024, a 15 mm version, which may be an ideal substitute as I imagine it would sit at the correct height if one simply tosses a small ball bearing into the knob before inserting the encoder shaft.

PEC11R-4225F-S0024, a 25 mm version, which will leave the knob sitting 8 mm too high. This may be ideal if someone would prefer to cut the shaft to the correct length, but that seems like a huge pain in the ass to me, so I don't recommend it.

I am vaguely aware that others have since found encoders which fit better into the Micron than the one I used in mine, but despite having a notice here advising people to send me links for years, I have yet to receive a link. If anyone would be so kind as to send me some part numbers I might list them here, particularly if you can report long-term success with the replacement part you used and supply links to web sites where it may be purchased. This is by far the most popular web page on my web site, and so I am sure that many others will appreciate your contribution.