Casiotone MT-68 won't power on

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Hi there, just found this forum and first post....

I have a Casiotone MT-68 that won't power on. I'm using a 7.5v mains power supply which works fine on another Casio SA21 keyboard that I have. When I use it to power the SA 21 the led on the power supply stays on as I would expect. But when I use it to try and power the MT-68 then the PSU led goes off when I switch the MT-68 on. I am assuming the MT-68 is centre negative which is the case with the SA21 but I have tried the PSU in centre negative and positive positions but the MT-68 stays dead and the power on led on the MT-68 never comes on.
I haven't tried to power it using batteries as I don't have any D cells. I have opened it up and poked around with a multimeter and the power switch seems to be registering 7.5v so it looks like power is getting in to the unit but I get a bit lost after that.
Can i ask if anyone has any experience with the MT-68 and is you could offer any advice on getting this keyboard up and running?

Many thanks for any help
 

happyrat1

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If you've hooked it up to reverse polarities already, then congratulations!

You own a paperweight.

Sell it on ebay for parts.

Gary ;)
 
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Hi, I was hoping this wouldn't be the case as there is no indicator on the power input to show whether the centre pole should be positive or negative. I've plugged other devices in with accidental wrong polarity before and they've been OK but I guess that's maybe device specific.
I just tried powering it with batteries and it still wouldn't power on, although I also noticed that there is a big 16v 2200uf capacitor on the board next to the power socket which got very hot with the batteries and I figure that could be an issue too?

Thanks
 

happyrat1

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That cap is now shorted plus god knows every electrolytic on the board and probably a few chips as well.
 

happyrat1

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BTW, Casio doesn't put reverse polarity protection on their older boards.

In fact, even nowadays I don't think they do either.

Gary ;)
 
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Thanks, I think I've found that out to my cost. I might try changing that capacitor, but otherwise I think it's now a dud :(
 

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