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 Post subject: Minimax ASB encoder needed
PostPosted: Wed Nov 26, 2014 3:44 am 
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Joined: Tue Nov 25, 2014 5:41 am
Posts: 1
Hi Guys, i'm new to the forum & new to the Minimax ... the Encoder has stopped working so any ideas where i can buy a new one???

it's the pot coming out the front bottom left next to the lights...


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 Post subject: Re: Minimax ASB encoder needed
PostPosted: Mon Dec 01, 2014 8:29 am 
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Joined: Mon Nov 15, 2010 12:57 pm
Posts: 1452
Have you opened the ASB to see the encoder? I would guess Mouser or Digikey have something that is similar. Seeing the pins, pin placement, or better: a manufacturer's part # would be good.


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 Post subject: Re: Minimax ASB encoder needed
PostPosted: Mon Dec 01, 2014 10:08 am 
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Joined: Fri Apr 01, 2011 4:49 am
Posts: 935
it depends if it is an rotary encoder or a potentiometer

rotary encoders fail much more than pots as they use a pulse system and over time they fail and start to jump you can add caps which slew the pulse so that it can read it properly

if its a pot very rare they fail they do get scratchy but because it is a conductive disk generally they can be cleaned even taken apart cleaned and put back together

now a pot will just be a voltage divider based on a scale log or linear it has a reference voltage and ground connection and a wiper the signal through the wiper is the reference voltage to ground

usually its a 5v signal and a sample and hold multiplex which samples the voltage and send the digital information to the processor

i dont know what the minimax uses but on most synths new and old they use a logic 4000 series chip in this case the 4051 variety these are 8 channel sample and holds

now you need to first find out if it is a pot this will be easy to tell as most use 10kb pots for this and will have 10kb written on the base of the pot

now if its a rotary encoder it gets more difficult as you need to know how many pulses it works to and sends

one way to know if pot or rotary encoder is a pot will only have a min max level

while a rotary encoder does not it just rotates in 360 degrees there is no stop usually but there are some that do have stops


a way to check if the pot is working correctly is to test the wiper when you move the slider the voltage should go from min 0volts to max 5volts you need a tester for this set to voltage

if it does not then you have a faulty pot but if it does work then the problem is then a component failure on the control section

the problem is there are no schematics service manuals released for the asb range so you will need to have a good electronics engineering background and be able to reverse engineer the circuits by testing and following and tracing the circuits a logic analyzer and a scope is a must as you need to test ic,s you will also need to track down the chips used as you will need the pdf spec sheet to see the voltage and timing signals for the ic so you can check on the scope that the chips are performing correctly


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 Post subject: Re: Minimax ASB encoder needed
PostPosted: Sun Jan 04, 2015 5:42 pm 
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Joined: Sat Jan 03, 2015 10:15 pm
Posts: 5
Here's the little i can contribute:
The same encoder had stopped working on my Pro12 ASB, and my tech was able to replace it, just looking at the type of encoder and mounting an equivalent one. So it shouldn't be too difficult.


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