Casio Keyboard Power Supply Part

Thread Starter


Joined Oct 3, 2017
I have a passive component on my power supply. Component looks like a disk capacitor and is marked "222". It has three leads, the outer two of which are insulated with rubber/foam. I'm not sure what this component is. I thought it was a thermistor, but can't find a thermistor with three leads. My keyboard suddenly died, and I think this part is responsible, but I can't find the part on line. Any help would be appreciated. Thank you. Fred


Joined Oct 2, 2009
Hi Fred, Welcome to All About Circuits. We are here to help you if you can help us to help you.

It would help if you provided more information than what you have posted.

For starters, what is the model number of the Casio keyboard?
Have you searched for a Service Manual or a copy of the circuit schematic?
What evidence do you have to make you suspect any specific component?

Show photographs of the internal boards of the keyboard and a closeup the your suspect component.
Also show us the component as located on the board so that we have an idea of the part of the circuit where it is used.

Thread Starter


Joined Oct 3, 2017
Thanks, Mr. Chips. Here's the info: model is Casiotone CT- 640 (old, I know).
I have called Casio technical support. They won't help with on-line or suggestions. I have looked for
repair manuals. Can't find any.
I have buzzed out all three leads of the component: all three leads are shorted together. There
is another similar component. I buzzed that out: two leads were shorted, but one wasn't. So I think the first
component is defective. At this point, I'm on a learning-curve and would really like to know 1) what this
component is and 2) if it has failed. Thanks. I will post a picture of the part as well. It looks like a ceramic
disk capacitor with three leads, the outer two of which are insulated. Part is stamped "222".


Joined Oct 3, 2017
Oh man I'm new here but I'm gonna have fun learning ...
and maybe helping if and when I can...
A photo/pic of the circuit will be excellent help.
Also on the circuit board look for the I.D.
Like the model (the year/date) all that info REALLY helps.
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