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Synthesizer key repair

Picture of Synthesizer key repair
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I have Yamaha PSR E 403 Synthesizer ( Image-1) using for the last 4 years. I found some keys are not working. So decided to repair at home.

1) First I marked the keys which are not responding by marker pen.
2) I opened up the keyboard from back side.
3) I observed the working of the mechanism by playing the keys in open condition, When you hit the key it presses the rubber key  
    pad.  ( the other end of the rubber key pad has has projection on which carbon film is deposited for electrical contact) (Image-6)
4) When we press key it makes Rubberized carbon film contact with the PCB tracks and shorts electrically. (Image-4)

5) I found in most of the keys, carbon layer was vanished (Image-9)and in some cases PCB tracks are not clean hence not
    making electrical contact.(Image-5)
6) Those PCB tracks are cleaned by brush and Isopropyl alcohol.
7) I got the old synthesizer, I removed its rubberized contact strip.(Image-7) made small round pieces (Dia 3 mm). (Image-8)
8) Then these pieces are fixed over damaged Rubber contact by instant Adhesive. (Image-9)

   After reassembly found all the keys are working fine
   Its a great pleasure but requires patience, It took 3 hours to fix 6 non working keys.
MikB1 year ago
WD40 is not a cleaning spray. It has almost no place inside electronic equipment, especially switches, pots, faders and contacts. It is designed to leave behind a film of oily greasy stuff to keep water away. 1) There's no water in your keyboard (I hope!) 2) This will attract dust and dirt in the future.

To clean those pads/tracks you need either water and detergent, and make sure it's dry after. Or IPA (Isopropyl Alcohol, Isopropanol) which will also help shift the dirt/grease.

This is the same sort of problem that afflicts remote controls, oily goo builds up on the circuit board and stops the buttons responding. Clean and dry is what you need, not greasy.
nachiketa (author)  MikB1 year ago
Thanks
for your suggestion, I opened up again the unit and cleaned with Isopropyl alchohol
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