Digital volume knob fix

The volume knob in my wife’s Toyota Highlander behaved weirdly.  As you turned it up or down, the volume setting would jump up or down, sometimes in the wrong direction and by an unpredictable amount.  It didn’t give a linear output as you would expect.

What to do?  Why, take it apart of course!

So first a bit of background.

The Land Before Time

In ye olden days everything was analog, as sinusoidal as ocean ripples.  Volume knobs were merely variable resistors (or “potentiometers”) that were connected directly to the output from an amplifier of a stereo system.  This would then directly attenuate — i.e., vary — the sound before it was sent to the speakers.

damped audio output

The Brave New World

In the future however, knobs have become digital, along with everything else.  They don’t alter the sound directly though.  Instead, they simply report their direction and perhaps speed to a microprocessor inside the amplifier so that it can make decisions about sound amplification.

One benefit with such a new-fangled knob is that there doesn’t need to be a hard limit on either end of its rotation.  You can turn forever and you’ll never get to the end of the rainbow. Why is that?

Because again, a digital “pot” 1 only outputs direction of rotation, not “amount” of adjustment or position of its rotation. In other words, the volume  is really just a software abstraction now.  It’s a parameter that the amplifier determines by itself based on the user turning the knob one way or the other.

Another advantage of the digital pot is that now it can vary several qualities of the amplifier.  No longer is it tied only to volume; now it can do sound fade and equalizer adjustments.  Really, the possibilities are near infinite since it’s so heavily tied to software.

A big downside is that these babies can get dirty inside just as easily as an old fashioned analog pot.  Even worse, they are way harder to clean than their ancestors.

Overall, I got really lucky on this project.  Pulling a stereo — especially a factory model — can be a real bear.  But as it turned out, the volume knob in question was connected to a little circuit board which then had a small ribbon cable which connected it back to the main amplifier board.  I was able to remove this little subassembly rather easily and do all the hard solder work back at my bench.

The next hardest step was to remove the digital pot completely and clean its contacts thoroughly. Not easy with just a soldering iron, but not impossible.

Afterward, the knob works perfectly!

Project Gallery

Video References

Below are some videos of others doing much the same cleaning process as I did.

Update!

A reader contacted me about his Highlander knob that had broken.  He found on some forum that a replacement part from Alps Electronics could possibly work.  That part though has had inventory shortages.  I did some research and found a suitable replacement from Mouser:

Footnotes

  1. short for potentiometer

8 Replies to “Digital volume knob fix”

  1. I was wondering if you managed to find the part number of this volume knob, I have the same stereo and the knob is totally broken, I am trying to find a replacement but can’t find the model or part number of this.

  2. I had a problem where the tuner shaft broke at the base and was hoping to find a new shaft piece that I could then use to replace the broken one. But the ones I have seen suggested (EC11E15244G1) do not seem tall enough to work (I measured the existing one that is approximately 32mm in height, and it seems at least 50% taller than the EC11E’s height. Anyone had any luck tracking down a replacement shaft, or the chip/shaft combination? Thanks…

    1. I used P/N 688-EC11E153440D from Mouser to replace a broken volume encoder on a 2008 Highlander non-navigation JBL stereo. The new encoder shaft is 20mm long vice ~30mm, but it works perfectly – the plastic press on knob just sits deeper in the well, making it better protected IMO. Mouser has 398 in stock and they’re $4.13 U.S. at this writing.

  3. After hours searching on the internet, I came up with a fix in my case (where the encoder/stem broke off at the base). Rather than buying a whole new radio (as the dealer suggested) or getting an encoder that didn’t look like it would fit), I realized that my stem piece, if held by hand, would still seat in its proper place. So I found a tight-fitting washer that fit around the encoder, and super glued it to the tuner unit such that it would hold the encoder in place. Seems to be working, though only time will tell…

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