A noob potentiometer question  [SOLVED]

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Jojo
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Post by Jojo »

Hi!

I'm attempting to repair a Mr Black Supermoon pedal which has three potentiometers.
One pot has obviously gone bad and measures infinite resistance between middle and outer terminals.
So I'll just replace it...

However, there is one thing I don't understand...

All three potentiometers are marked B50K. The way I read it they should be linear 0-50k Ohm pots.
The two working pots both measure about 2.5k Ohms between the outer terminals.

Shouldn't they measure 50K?

Thanks for your input!

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bow_and_error
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Post by bow_and_error »

Did you remove the pots before you measured them? If not, you're bound to get weird readings as there are other components & ground interacting with the pots.

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ppluis0
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Post by ppluis0 »

Hi Jojo and welcome to this forum.

Could you post some pictures of the pedal since you have taken it apart?
Mr Black's printed circuit designs are characterized by being very well designed and it would be nice to be able to see the inside of one of these devices here in the forum.

Cheers,
Jose

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bmxguitarsbmx
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Post by bmxguitarsbmx »

ppluis0 wrote: 26 Apr 2021, 20:58 Hi Jojo and welcome to this forum.

Could you post some pictures of the pedal since you have taken it apart?
Mr Black's printed circuit designs are characterized by being very well designed and it would be nice to be able to see the inside of one of these devices here in the forum.

Cheers,
Jose
His pcb designs are symmetrical.

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Jojo
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Post by Jojo »

Image

Image

Image

Image


Yes I did the measurement in circuit. So that explains why I got "wrong" readings. There are parallel resistances that lower the resistance at point where I was measuring. Thanks for your answer! :)

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Jojo
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Post by Jojo »

I've often wondered if it could be possible to clone a device such as this pedal, if there is any programming involved of the ICs?
Or could you just order the same IC solder away and it would work?

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ppluis0
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Post by ppluis0 »

Jojo wrote: 27 Apr 2021, 11:38 ...could you just order the same IC solder away and it would work?
Nope.
The 8 pin IC that appears in the third image is a memory that stores a program.
The bigger chip is a digital processor that create the desired effect.
There are some programs ready to use: http://www.spinsemi.com/programs.php
And the link to explain programming: http://www.spinsemi.com/knowledge_base/pgm_quick.html

Cheers,
Jose

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Jojo
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Post by Jojo »

So it could be a pre made program like the ones you linked, or a modded program or an entirely propriety program.
Very interesting, thanks Jose!

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Post by ppluis0 »

Perhaps exist in several places of the web more programs for this line of signal processor IC's
The couple of links posted were the first that appeared after googling, so I think that more libraries can be found.

Cheers,
Jose

BTW: did you have images of the bottom side of this board ?

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Jojo
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Post by Jojo »

Image

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