"Gareth Magennis" wrote in message
...

"N_Cook" wrote in message
...
Gareth Magennis wrote in message
...


"N_Cook" wrote in message
...
Getting a bit flakey on a Behringer SL2442 mixing desk.
Just 3 control lines out , ground and 2 lines taken high via 4K7 to
5V.
What
would be inside , 2 sets of 10 resistors? All wrapped up again ,
different
problem repaired and only noticed at final checks so cannot
investigate.
Owner only uses one effect so fingers-crossed will not need
replacement
or
its fellow




The ones I've seen have 2 printed concentric zero ohm tracks, in a
"square
wave" pattern.
Each track is supplied with 5v by the pullup resistors, the wiper
shorting
out the tracks as it is turned, producing 2 square wave outputs.

The tracks are printed such that turning it one way makes one output
lead
the other, turning it backwards makes it lag the other.

It is then possible to use these as data lines to a uP port, where
software
determines direction of rotation and increments or decrements a counter
to
show how far it has been moved.

Obviously it is not possible to determine absolute position.



Gareth.


And then non-volatile memory storage of the last stored position . So
presumably you can turn the control when powered off and it will display
the
stored setting when powered on again.
So there is a good chance of getting inside one to clean etc and return
it
to productive use .




My experience is that mostly when they go dicky you need to replace them.

You can get away with a bit of a crackly pot, but not a misbehaving Data
encoder, where often they will only go one way, or jump several positions
at once and be almost impossible to home in on the right spot.
This pretty much renders them useless unless perfect.



Gareth.

Interesting that you've found that. I have had total success cleaning the
ones that are fitted to hifi's, for years now. The rotating encoder rings
and the wiping contacts are normally gold plated, and the intermittency
issue is caused by the 'stirring treacle' grease that's used in them,
migrating down the shaft and onto the contacts. When removed from the pcb,
these encoders are easily stripped. A little drop of IPA on a cotton bud
turns the grease to a sort of 'jelly', which is then easily picked out with
tweezers. Once it's all clean, I normally retension the contacts, and add a
single drop of cleaner / lubricant before reassembling. I can't recall ever
having to replace one, and have done scores of them over the years. It was a
favourite problem in many of the Aiwa models that were on the market a few
years ago.

Arfa