[How To] Add a center detent to a 9mm potentiometer.

[MrBinns]

I made an imgur album: http://imgur.com/gallery/i0UNI

Ahh! I don't know how to resize images. I just posted the url for each pic instead. if you don't want to look at the album for what ever reason.


http://i.imgur.com/KNVLVkc.jpg
Alpha 9mm potentiometer with 11 detents from smallbear electronics. There are two rivets holding everything together.


http://i.imgur.com/GgzB0gG.jpg
Start drilling the rivets heads out. I used a 5/64" drill bit. It doesn't take much.


http://i.imgur.com/RKtYDoX.jpg
With the rivets out.


http://i.imgur.com/G7YSFQ7.jpg
Here is a shot with the bottom plate off, and the wiper pulled out(white plastic and metal piece at the bottom). On the right is the top plate with the shaft still attached.


http://i.imgur.com/5sUjT86.jpg
You need to remove the piece outlined in red. I'm going to refer to it as the "control piece" because it connects the shaft to the wiper and it also keeps the shaft from spinning all the way around.


http://i.imgur.com/RKkJOs2.jpg
I did this on the concentric pot first, but you can use the same technique for the other pot. Although I recommend prying it off with a small screw driver.

Here I used a flattened nail and hammer to hit the shaft while holding the control piece with vice grips.

What is left is a metal retaining disk.


http://i.imgur.com/VE5nN6T.jpg
I just used a small screw driver and ever so carefully pried it up, moving in a circle until I came off or I could pull it off with needle nose pliers.  Be careful not to @#$% this piece up. It's very thin and flexible.


http://i.imgur.com/AVPlcfJ.jpg
The shaft pulls straight out and the top section can come off.

Note the dove tail on the control piece and the square plastic protrusion on the inside of the green piece. The dove tail bumps up against protrusion and prevents the shaft from spinning all the way around.


http://i.imgur.com/vPS6U6z.jpg
I tried to use the same technique to remove the control piece for the top section but ended up knocking the pot out of my vice grips. I broke off one of the small tabs that goes into the wiper and messed up the other one pretty bad. Again it should pry off with a screw driver. Work it around until it comes off.  


http://i.imgur.com/WQboxsF.jpg
Here is a pic of all three retaining pieces. On the bottom is the retaining piece for the top section of the concentric pot. It is attached to the control piece and must be used for that section. On the right is the retaining piece for the bottom section of the concentric pot. The one in the middle is for the pot with 11 detents. You can see the small indention on the top half


http://i.imgur.com/g2BHvN4.png
Top plate with both shafts removed.


http://i.imgur.com/OhQSLRW.png
Here is what the top plate of the 9mm pot with 11 detents looks like. The retaining piece has a small indention in it that falls into the detents. I took this pic after I changed the concentric shaft for the normal shaft.


http://i.imgur.com/BhRUQyr.png
To get the shaft to stop at each detent I indented the retaining piece with small flat head and hammer. The location of the indention is important. Maybe not if you use the top plate with 11 detents because the go all the way around, I'm not sure if it matters with this top plate. but...


http://i.imgur.com/TbjHfTt.png
Here is a pic  of both top plates.


http://i.imgur.com/YmJyVbx.png
After removing the copper disk. A wild center detent appears!

So you don't have to use the top plate with 11 detents you can just remove this copper disk. If you do use this plate the location of the indention on the retaining piece matters because of the dove tail.

You can do this to the top plate and bottom section. You can also swap sections. I swapped the 25K from the normal shaft pot with the bottom 100K section.

To put it back together just reverse the steps and make sure it fits correctly. I plan on putting a small drop of super glue on the rivets to hold them in place, after pushing them through. I should be able to scrape the glue off if I need to take it apart again.