Casio CT-460

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Howdy,
I was recently given a broken Casio CT-460 home keyboard and I'm hell bent on fixing it. However, I can't find a schematic anywhere for this thing. So, if anyone has one or knows where I can find one that would be greatly appreciated. The user manual leaves much to be desired. I would also like any broad diagnosis you can offer. Here's the problem, when I play any sound on the board it is very very quiet and overwhelmed by static. This happens in both the speakers and through the output. I can here the tone under the static but it's very faint. I opened it up to look for obvious damage (blown capacitor, corroded wire, etc.) And everything looks tiptop as far as I can see and test with a LED.
Now, I'm aware that this is a cheap home keyboard and some of you might say trash it. But, I really like the cheesy 80's sound this thing has and I really would rather fix it than seek out another.
Thanks in advance!
 
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If you have the electronic test gear then you may stand a chance but as you can pick up something like the 460 for about $50 then buying test gear and spending hours working through it just does not make sense.

Service manuals are available but they can cost and I am not even going to search for them myself as the 460 is not worth the effort.

Buy a working unit and spend the time playing.
 

happyrat1

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First thing to check is the electrolytic capacitors.

Given the age of the board they are probably starting to leak.

Check for bulging caps.

Ideally you use an ESR meter to test the caps in circuit.

Gary ;)
 

happyrat1

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Also the static could be caused by a dirty volume pot. Squirt a little contact cleaner into the pots and give them a few twists to clear up that problem.

Gary ;)
 
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Thanks for the advice Gary! I'll try the contact spray. To the eye all caps look great. Is it possible that a computer chip is fried? I'm honestly not sure how to test that one.
 

happyrat1

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Caps can leak current internally without displaying visible symptoms. The only way to be sure is to test them out of circuit with a DVOM with Capacitance Ranges or in circuit with an ESR Meter.

Also forget about the CPU. If CPU were fried it wouldn't even light up.

Last thing to check would be op amps and audio transistors in the audio chain.

They could be failing and become noisy.

Gary ;)
 

happyrat1

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BTW, Electrolytic caps have a tolerance of about +/-50% so you just need them to test in that range.

Gary ;)
 
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Gotchya! Thank you, I'll get to testing.
You wouldn't happen to know where I could find a schematic for this thing would you?
 

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