Gareth Magennis wrote in message
...


"Arfa Daily" wrote in message
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"Gareth Magennis" wrote in message
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"N_Cook" wrote in message
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Gareth Magennis wrote in message
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"N_Cook" wrote in message
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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


These are the type typically found in Mr Cooks mixer, FX units etc.


http://uk.farnell.com/alps/ec11e0920...18det-9ppr/dp/
2064980

At £2.05 for a new one I am certainly not going to bother trying to bodge
a
few extra months out of a knackered one!
(The official parts from manufacturers (Yamaha, Roland, Korg etc) can
admittedly sometimes cost up to £10 after postage/packing etc)

But that's more my policy than anything else - Do I charge the customer
labour for bodging, or do I, in my opinion, do the right thing and replace
the faulty part instead?
If the customer finds it goes dicky again less than a year after I've
charged him at least an hours labour to supposedly fix it, my reputation
is
going to take a hit.

With a new one, it feels all nice and new again, its easily within an
hours
labour plus parts, the customer is well chuffed, and it should last the
same
amount of time again.
No brainer, IMHO.


Cheers,


Gareth.


This one has a co-axial switch for the memory change function and as far as
I remember no where in that 2x3 foot panel , any space to squeeze a switch ,
apart from having to cut a new hole in the top pannel.
So recondition of the existing or constrained to the main-dealer for supply
of a direct replacement