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Rusty, Music Professional
Category: Electronic Musical Instruments
Satisfied Customers: 6059
Experience:  Sound Engineer, Electrical Issues, Tone Consulting
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I recently bought a replacement "trigger" PCB (KKB 008)

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I recently bought a replacement "trigger" PCB (KKB 008) following a fault with a couple of keys on my kawai mp 9500
I have fitted the new board however one of the keys #43 is triggering at a higher volume compared to the other 87 . Aftertouch and sustain is correctly working etc. I'm not sure whether this is a faulty replacement as I purchased from a reputable spares provider. Is this a common fault? Can I manually programme the volume of an individual key which will fix the fault ? My only other option is to return the part back as faulty. Regards Brian
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In the piano, where the keys strike, there are velocity sensitive pads that can wear out. When they wear out, they either lose their velocity sensitivity, or they quit sounding altogether. Pads are a maintenance item, and are relatively inexpensive and simple to replace. You're going to have to remove the cover again.
Notice where each key hits when you strike them. Those are the contact strips that will need to be replaced. Since you've done some repairs already, you may consider replacing all of them, but it's not necessary. Order a spare in case another key goes out.
Once you replace that pad, the velocity will return, and you'll have a fully working piano again. Let me know if you have any trouble.
Customer: replied 2 years ago.
Thanks for the swift reply Rusty but the rubber contact pads have also been replaced at the same time.
I will replace do a swap around of the contact pad to eliminate it as it's possible that the individual rubber is flawed or damaged.
If this is not the problem , is it possible to programme the volume of an individual key? Yes I agree that this would be a workaround. My other option is to swap the hammer for a lighter one at the higher register end which isn't ideal.
Back to my original question, is it likely that the soldering is flawed on the PCB ?.
A number of questions asked which I'd appreciate you can answer.
Nope, not at all. Those contact strips are what control the velocity sensitivity. Are you able to get any velocity from the key at all, or is it always the same loud volume?
Customer: replied 2 years ago.
Yes the velocity is working to a large degree ..average.triggered velocity is however higher for this contact or key compared to others which are more dampened. If I light touch the action it brings it down which tells me that the parameter of the velocity appears to be ok.
The average initial trigger velocity is where I'm having the problem!
That still sounds like a bad pad to me... A solder joint only makes a connection; It's either connected, or not connected. That rules out the solder joint.
Your tone generator is triggered by each of those pads. It will not produce more or less of a sound on its own, it's controlled by the pad.
You have a master reset on that piano that will adjust any settings back to the factory so we can rule out a setting. Press Store. Press the menu up button repeatedly until you see RESET ALL. Press the value up button twice, and it will reset.
If it still has the problem, you received one bad pad on the contact strip. You can swap them with other pads to make sure, but I believe that is where the problem is hiding.
Customer: replied 2 years ago.
Thanks. I will therefore try this first tomorrow and let you know how I get on before I close the case.
Sounds good, let me know what you find.
Customer: replied 2 years ago.
Hi Rusty
Just to let you know that I followed your advice and you were correct. It was a faulty contact pad! despite it being new.
So thanks for the advice. It has saved me considerable time and all is working properly.
Best Regards
You are very welcome Brian. All signs were pointing to a faulty pad. I'm glad we were able to get it working so quickly. Let me know if you have any other questions.
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