Vintage Casio Keyboard Overvoltage Repair

[popovm]

Casio forum post

First time posting here and I hope this is a good fit for the forum. I am looking to get some help with repairing a keyboard that I just picked up from a thrift store. I have always thought the sound from these little Casiotone keyboards was cool so I thought I would take a chance on it. I did notice that someone had used a 12 volt (if I an remembering correctly, it may have been 15) power supply to try to test it out in the store and it only requires 7.5 vdc, per the markings on the case. I tested it out with batteries and it just makes a pop sound through the speaker when I turn it on.

How would I go about trying to fix this? The board looks to me to be simply made and I have always wanted to learn soldering. I have been researching and I have been seeing that capacitors can go bad in this scenario. Should I replace all of those? I have read the same about diodes. I have included a pic of the components and the traces on the back in case that helps. How likely is it that the ICs are damaged? Sourcing ICs would probably be beyond the amount of effort I would like to put into this, so I am hoping that isn't the case.

https://onedrive.live.com/redir?resid=E4254ECA6498DB59!1647&authkey=!AFiUGHkbgwz3VwI&v=3&ithint=photo%2cjpg

https://onedrive.live.com/redir?resid=E4254ECA6498DB59!1648&authkey=!AKHGYLxxRd6Td7E&v=3&ithint=photo%2cjpg

Sorry, having some trouble figuring out how to embed.

 

[Ralston18]

Could not see the pics per whatever embeding problem occurred....

Being hit with double the design voltage may have pretty much fried the keyboard. And there is no knowing the previous history and possible abuse that the keyboard may have been subjected to.

Anyway restoration could be a fun project but I would first go over the circuit boards with a good, strong magnifying glass under bright light and look for any signs of overheating, burning, sparking, etc. Probably a dark brown to black coloring on or around a component. May spot cracks in the circuits or broken solder joints.

You could use a multimeter to check the component, capacitors, resisters etc. and see what those tests indicate.

Something you will need to learn to do (if you do not already know) so you can check your soldering later on.

IC's are much trickier but may be testable if you have the specifications.

Depending on your overall ambition (and level of effort limit) you may be able to find an identical keyboard that does not work and combine the two into one working unit.