I have a casio kct-671 it works but sometime it gets a high frequency tone from the speakers and won't respons eny key. Untill i shut down an power the keyboard for x manny times then it works again.

SOURCE: Casio CTK-671 No Sound

Try plugging in a set of head phones , if you get sound that way the input jack may be causeing the prob. try pulling it back an forth a few times, sometimes this will free up the head phone jack. I hope its that simple . May be some one will have another idea Good luck DFD please rate me TK U

SOURCE: What kind of power source/adapter do I use for my Casio tone bank

Take a close look at where the power source adapter plugs in, there should be something written which will indicate the voltage requirements, write them down, for example it might indicate +plus or minus 12 volts DC at 400 Milliamps. Take the info you write down to Radio Shack and they should be able to sell you a universal power adapter that will work. You should have a power on-off switch some where on the unit.

SOURCE: NO power to my Casio CTK 671

OFTEN the power connector in the synth get broken from the circuit board connections.

ALSO verify the adapter is actually putting out the correct voltage or slightly above it..

SOURCE: NO power to my Casio CTK 671

First verify with a voltmeter that the adapter IS producing the voltage it is supposed to.

The cords and internals of these often fail.

Anything beyond that will require servicing. One could oppen the unit and look for bad solder or cracked board NEAR the power input jack.

SOURCE: need power cord for Casio CA-100 Tone Bank

You need a 9 volt DC adapter with at least 850ms (0.85 amp) capabilty with the center the minus polarity. A good place to find thes is thrift shops, but DO be careful that the center is the MINUS polarity.