The NCE Power Cab is a popular DCC controller for model railroads. But one vulnerability it has, is the reliability of speed controller wheel (also called thumb wheel, or rotary encoder). For many people, after some time of use, the thumb wheel started working erratically, not responding correctly to the thumb wheel movements.
The controller is still useable, there are speed buttons that can be used instead of the thumb wheel. If the controller is still under warranty, the manufacturer will replace the encoder, but the controller would have to be shipped out for the warranty repair, and I assume one would have to pay for the shipping.
Doing the repair yourself
One option is to replace the encoder yourself. That’s what I did, when the thumb wheel on my controller went bad.
If you have basic electronic soldering skills, it is actually quite easy to replace the encoder. You can find the encoder at various retailers online.
The technical name of the replacement encoder which I found online, is “Rotary Encoder, Mechanical, Incremental, 6 PPR, 0 Detents, Horizontal, Without Push Switch”.
Ordering the replacement part
This encoder is manufactured by Bourns, part number 3315C-001-006L, and can be found for sale at various online sites. I purchased mine from the Newark online store. The item cost for the encoder is quite low, much less than the shipping cost. I ordered a few extra encoders, for the same fixed shipping cost, that way I will have spare encoders. At the time of this writing, they were sold out on the Newark site, but they might restock them, or you can look for the encoder on other sites online.
I don’t know if there might be other versions of the encoders for the controller, for example newer versions. I recommend that before you order a new encoder, to take your controller apart, and confirm that your encoder has the matching part number.
Replacing the encoder, step-by-step instructions
The Power Cab controller comes apart very easy: unscrew the 9 same-size screws, remove the bottom cover, and then the circuit board from the top cover.
Remove the encoder by de-soldering the 3 pins on the backside of the circuit board (use a solder suction tool, or other appropriate method, to remove the solder).
Pull the thumb wheel off the old encoder, and install it on the new encoder.
Install the new encoder, and cut off the excess contact prongs. Assemble the controller in reverse order. Finally, test the controller, to ensure everything works, and you are all set!