How to correctly identify potentiometers for midi cc on my Axiom 25

Thread Starter

santixolas

Joined Feb 25, 2022
2
Hello guys

So, my axiom 25(midi keyboard) pots are faulty. So After trying the cleaning method i opened the keyboard, desolder the pots, measure them (10k) and order some new ones (PTV111-1415A-B103) so i thought!

https://pt.mouser.com/ProductDetail/Bourns/PTV111-1415A-B103?qs=okKRLHKnSlan/x7xrUU2XQ==

Now, it is no working properly... the range is very short on both. when assembled in the keyboard instead of the 0-127 range i get 50-80.

Need to mention that the potentiometers when mounted on the wheel only use 1/3 of the total travel

You would expect them to have a lower resistance like 5k for example but they don't even exist in these models in the catalogs and in addition to that when measure the old ones they are 10k...

Either it's their resistance curve or I'm missing something?


I used those pots because they are linear and that made some sense to me. But now i'm wondering if they are logarithm??

A didn't found any schematics on web and even opened some tickets at m-audio support but nobody replied

Can anyone with knowledge of electronics help find the pots i need for the keyboard?

By the way...beside the "b103" number which i think that are the resistance number (10k) what are the other number reference? the pots that i've bought didn't had any.

i'll leave a photo of them (the olds and original ones) and the datasheet of the ones that i've bought.

axiom 25 pots.jpg

Best regards to all
 

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Ya’akov

Joined Jan 27, 2019
5,683
Welcome to AAC.

It is very possible the originals were audio taper. You can roughly graph the curve from one outside leg to the inner wiper leg with a DMM and careful equal rotating steps.

Do the new pots measure 10K across the outside terminals?
 

Thread Starter

santixolas

Joined Feb 25, 2022
2
Do the new pots measure 10K across the outside terminals?
Yes they are 10k.

It is very possible the originals were audio taper. You can roughly graph the curve from one outside leg to the inner wiper leg with a DMM and careful equal rotating steps.
i've somehow tried but since the old ones gave me all scramble info, jumping around in all sort values i didn't get any certain of the readings.

thanks for you quick reply.
 
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