Yamaha A3000 Hacking: Knobs Befudgery

Short answer:

Replacement rotary encoders exist but can't be purchased in small quantity.
Instead, use a good contact cleaner like Caig DeoxIT on the encoders and they'll be like new. (you can get it at PartsExpress)

Long answer:

Attempt #1: Knob replacement

My A3k has had wonky knobs (aka "rotary encoders") ever since I bought it second-hand from some sound designer. They managed to get worse until about a year ago when I eventually got so sick of them that I just stopped using the little blue box. Most of the encoders would either work not at all when spun at any speed or a single-click nudge would cause them to register a 10-20 click movement. Very frustrating when you're trying to just turn on or off a boolean value, let along scrolling through some 0-127 value range.

Recently, I decided to try to find replacements for the rotary encoders, since I believed them to be totally unfixable. Initial inspection of the rotary encoders showed them to be very small and tightly sealed. I had to desolder one to determine that the encoder was an Alps part.

But the encoder was so small that there wasn't any room for a part number, so I was out of luck for finding an exact replacement. I knew that rotary encoders come in all shapes and sizes, but that the small ones used in consumer electronics are usually mechanical encoders, not optical. (If they were optical, we probably wouldn't have any problems with them, since there's no contacts to build crud up on).

I measured all aspects of the encoder that I could and found that this Alps part matches pretty well:

After looking at literature for many brands of rotary encoders and measuring the encoder again, it looks like the most important attributes of the encoders are: The shaft length is a little bit negotiable. I found many more devices with longer shaft lengths, so if you don't mind your knobs sticking out more than normal, you can use those.

The "30 detents, 15 pulses" I've found to be very important to their functioning. Because of the way the A3k reads the encoders, the detents must be twice the number of pulses or the A3k will read the movement as being backwards and at twice the speed. I personally think this was a mistake on their part, since the detents are placed on the transition points of the output signals generated by the encoders, making them more likely to generate false outputs.

So anyway, here's a list of all the vendors and parts that appear to be good matches:

So I now had enough information to purchase a handful of these devices. I webbed and called around to the various electronic component distributors I was aware of:

Universally, these companies didn't have any, or would get them as long as I bought 1000 at a time. So, I'm basically stymied. Unless I can find 200 people who want brand-new knobs, that is.

So, with that, I was forced to find another solution.


Attempt #2: Knob cleaning

And I really did find a good solution. Caig long ago made a magical elixer called "Cramolin" that did wonders on fader pots and such. I had totally forgotten about it. If it works well on analog faders, it should work even better on digital encoders (which work similarly, by scraping a metal contact against a surface)

Caig doesn't make Cramolin anymore, but they make something the same or better called DeoxIT

The hard part about getting a cleaner into the crevices of these encoders that they are very tightly sealed and cannot be taken apart without destroying them. On a lark, I tried spraying between the small space between shaft and base (the needed gap so the push button part of the encoder will work):

I then worked the cleaner in by rotating the knob back and forth many times, both with the switch out and the switch pushed in. I then turned on the A3k, selected a screen with an adjustable parameter on the knob I was working on and worked it more. It began working better and better.

I don't think the cleaner harms finishes, so you can even apply it without taking your A3k apart:

But I would recommend putting a paper towel (as shown) underneath to protect any of your other equipment from the splatter.

Caig DeoxIT is god, long live Caig DeoxIT.

-=tod : 30 October 2000

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