Replacing the volume knob on a Kenwood amplifier
For some reason, repairing broken equipment is one of these tasks that I tend to put off for months, if not years, because it feels like it’s going to be a lot of hassle.
About a year ago the volume knob broke off my Kenwood KRF-V5090D audio video surround receiver during transport. For a while I was able to make it work again by gluing the parts back together, using a matchstick and some polyurethane resin. In the end, this didn’t hold though, and it became increasingly difficult to set the volume. Given that I bought the thing quite cheaply in a second-hand store and the remote control was missing, I decided to try and replace the volume knob myself. The amplifier is a member of the Kenwood KRF-V and VR series, which all seem to be similar (and mostly share the same remote control unit). The manual can be found on the Kenwood site.
Being a “digital” amplifier, the design doesn’t use a good old potentiometer for setting the volume. Instead, the volume knob is connected to an incremental rotary encoder. Unfortunately the ALPS encoder used by Kenwood is rather cheaply fitted with a hollow plastic shaft, which can quite easily break off at the base if sideways pressure is applied, which is exactly what happened. Annoyingly the encoder in question also doesn’t state a parts number, so it’s hard to determine what type it is. Some measuring and searching revealed that it must be either a 24-pulse EC12E2430803 or a 12-pulse EC12E1220813.
I went with the EC12E2430803 (a correct guess as it turned out), which can be cheaply ordered from Farnell, among others. Opening the amplifier case is easy, but removing the front print and desoldering the controller does require a bit of work and patience. Be sure to have a good look at how the pins are connected before you desolder them, as all three pins need to be connected (and after desoldering this can be a bit hard to see, especially if you somewhat damage the print while soldering, as I tend to do). All in all the entire procedure of taking the amplifier apart, replacing the controller and putting everything back together took about twenty minutes, which makes one wonder why I put it off for so long. Of course, looking up the controller type and ordering it took a lot more time, which is why I wrote this page. I hope it will be of use to someone in the future. :-)