In all octaves, some of the notes dont play.
Electronic keyboards use capacitors, for the individual notes, when you press the key's on the keyboard.
(There are other electronic components used in conjunction with the capacitors, but capacitor failure is the most common)
There may be more than one capacitor used for an individual note.
Electrolytic Capacitors.
Electrolytic capacitors can break down over time, and fail.
An Electrolytic Capacitor is essentially a small aluminum 'can' with the components inside.
There are three strips that are rolled up together, and inserted into the can.
1)One strip is a metal conducting strip. Thin as tinfoil.
2)One strip is a non-conducting strip. Made of thin metal also, and has a non-conducting coating applied to it.
3) One strip is a paper, and is soaked with Electrolytic Paste.
The paper strip is laid in-between the metal conducting strip, and the non-conducting strip, and all three are rolled up together.
The conducting strip has a lead connected to it. It's the Positive lead
The non-conducting strip has a lead connected to it.
It's the Negative lead.
The 'Can' has a rubber seal on the bottom. Envision a round rubber plug, that resembles a small plate, if you will.
The Electrolytic paste breaks down. When it does it forms a gas. This gas expands, and compromises the seal. Pushes an edge of the seal out of the can.
The 'Can' also has a shape etched part way, into the top of the can. Usually a X or lK shape. The gas can expand, and break this shape open.
(Example: The X shape pops open like fingers standing up. The areas in-between the X)
When this happens paste oozes out.
So much paste loss, and the capacitor operates at a lessor degree.
Too much paste loss, and the capacitor fails. Doesn't work at all.
Sometimes the paste just dries up.
To explain further about Electrolytic Capacitors, and their construction,
http://en.wikipedia.org/wiki/Electrolytic_capacitor
[The Electrolytic Capacitors used in computers, and electronic keyboards, are shown in the second photo down, on the right side. The capacitor on the bottom of the second photo, is what I'm referencing to.
Scroll down to the Construction heading also)
Solution to fixing this problem?
Replace the capacitors that have failed with the same capacitance.
(Same Microfarad rating, same voltage)
Problem is, you need to diagnose what circuit the capacitor, or capacitors are in.
The circuit that has the capacitors, that the notes do not play.
You may be able to do a simple visual diagnoses, for obvious signs of capacitor failure. If the paste has dried up inside the capacitor, there are no outside visual signs.
This link gives you info about Visual Signs of Capacitor failure. It is related to computer motherboards, but will crossover to all Electrolytic Capacitors of this style,
http://www.capacitorlab.com/visible-failures/index.htm
This is an example, of an electronic keyboard's circuit schematic,
http://www.musicfromouterspace.com/analogsynth/keybrdcontroller.html
This is information stated to give you a brief explanation, as to why certain notes do not play on your keyboard.
It is Not advice to repair it yourself.
I want you to be SAFE.
I just wanted to give you information to your problem.
HOWEVER, if you have soldering skills, and a decent background in electronics, you MAY feel comfortable in trying to fix the problem yourself.
If you Do Not see obvious visual signs of capacitor failure, you will need a circuit diagram to find what, or which, capacitors have failed.
To my knowledge, only the manufacturer of the keyboard has this info.
I have seen a few schematics on the internet, listed for various electronic keyboards. They are not free, however.
Other than this, you would have to remove capacitor after capacitor, and replace them one at a time, until the bad capacitor is found.
NOTE*
1) Power HAS to be removed from the electronic device FIRST!
2) Electrolytic Capacitors can hold a charge for weeks, sometimes months, after the power source has been removed!
As you can see by the photo reference I gave, there are two leads, or terminals, coming out of the bottom of the capacitor.
If your finger/s touch both of these leads at the same time, the charge stored in the capacitor will be released to YOU!
IF, your fingers touch a circuit that a capacitor is in, and your finger/s complete the circuit, the charge can be released to YOU!
Bad shock to fatal! Depends on the size, and voltage of the capacitor.
A tech will discharge the capacitors before working on the electronic device. I will not state here how to do this. One wrong move, and the capacitor could blow up.
(Using a metal screwdriver to discharge is NOT the way to proceed! NEVER do this!)
