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Weird problem with my CTK-5000


Modar

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Hello there.
So I've got a Casio CTK-5000 Portable Keyboard, and I noticed that when the Eb key on the 4th octave is pressed down, D; C; C#; B; Bb; A; Ab (on the 4th octave also) always play at the highest velocity (= 127) no matter how soft I press them, Even though I can't reach that velocity when pressing any key alone even if I wanted to (Max. = 100).
 What's wrong with that Eb Key? How do I prevent the mentioned keys from sounding really loud when the Eb Key is pressed down? 

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This is indicative of debris (cookie crumbs, cracker crumbs, toast crumbs, pizza crust, dead bug, hairpins, straight pins, needles, etc, etc, etc) under the keys - between the keys and the rubber contact strip under the keys, but that normally affects only a single key or maybe two keys right next to each other.  For one key to affect the velocity level of several other keys sounds more like a contact strip or circuit problem, but before getting into that, get a can of compressed air and try blasting it generously under the keys to see if that clears the problem.  If it does, then one of the items I mentioned at the start was probably the cause.  If it doesn't, then you may be looking at a trip to the service center.  The keyboard resets itself each time it is powered on.  The is no separate factory reset or initialize function.

 

 

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49 minutes ago, tnicoson said:

This is indicative of debris (cookie crumbs, cracker crumbs, toast crumbs, pizza crust, dead bug, hairpins, straight pins, needles, etc, etc, etc) under the keys - between the keys and the rubber contact strip under the keys, but that normally affects only a single key or maybe two keys right next to each other.  For one key to affect the velocity level of several other keys sounds more like a contact strip or circuit problem, but before getting into that, get a can of compressed air and try blasting it generously under the keys to see if that clears the problem.  If it does, then one of the items I mentioned at the start was probably the cause.  If it doesn't, then you may be looking at a trip to the service center.  The keyboard resets itself each time it is powered on.  The is no separate factory reset or initialize function.

 

 

A guy on Reddit suggested that the problem is caused by a faulty diode, this seems to be true since the total number of keys affected is 1 + 7 = 8 (a matrix). Any idea what type of diodes is used in these keyboards?

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You would need a service manual to determine that.  I am sure the CTK-5000 circuit boards use several different types of diodes, depending upon their particular function and current/voltage requirements in the circuit,  So the question is not only what type of diode, but which particular diode.  I recommend doing a Google search on "CTK-5000 Service Manual" to see if a downloadable version is available.

 

 

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