My mom gave my daughter Casio ctk551 keyboard adapter has power and we've tried batteries keyboard will not come on noticed a little rust on back plate took off clean with dry cloth nothing any sugges

Is it connected to any external devices?

This could be a loose plug inside the unit or it could be a circuit that is bad. If the plug failed it is from physical damage from something like tripping over it or heavy use. That can be repaired by replacing the plug. If it is something like a component in the unit on a board then it becomes a little more involved.

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HQRP AC Adapter / Power Supply for Yamaha PSR-280 / PSR280 / PSR-290 / PSR290 Keyboards Replacement plus HQRP Coaster, adapter related ... need a new one, you could try to get a replacement from casio or try to get an ... It MAY appear to operate on DC BUT it can't generate the +/- voltages internally for sound .

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If it hasn\'t been dropped or bumped, check the adapter. Work backwards from the keyboard. It doesn\'t take much for the casio adapters to pack a sad. If there\'s an overload in your switchboard, it\'s usually the Casio that packs a sad...everything else is fine, microwave, tv, stereo - just not the casio. Their adapters are garbage and until recently - they\'ve just gotten better

Some Casio Keyboards use 9V DC (center negative) others 12V DC (center negative).
If check what voltage your Keyboard use. Generic AC adapters are usually center positive. So you have to invert the wire with a new DC plug to make it center negative,
Easiest is to buy a Casio ac adapter made for your keyboard from a Casio retailer.

If batteries or power adapter does not power up the keyboard...possibilities are...if it has a fuse inside or fusible link check it.replace if blown.Another possibility is power component has a short. maybe from constant movement of power plug into keyboard.sometimes just by inserting the plug and wiggling it can solve the issue..having this fixed by a technician can cost a lot of money.but,if your keyboard`s value is less than the cost of fixing it,might as well replace your instrument.

The adapter has a problem... likely a poor connection of input power that briefly contacts building up some voltage that is then stored in the capacitors in the adapter which then discharge quicklly when you turn on the Casio. The adapters with FIXED blades OFTEN have problems contacting the connections in wall receptacles and extension cords. You may need to bend the blades slightly or use a better receptacle like connector. IF your adapter has a three wire cord from it to the wall receptacle, those SOMETIMES don't seat well...

Hi - look in back or under keyboard for power specs.Then go to Guitar Center and the right adapter. GuitarCenter.com has casio power adapters.

If you have a volt/ohm meter try checking to plug that goes into the keyboard for voltage on the DC setting. If there is none, you will have to replace the adapter. Be sure to plug the adapter into the wall when you check it or you will get no reading. If that is not the problem, then it is probably the receptacle for the DC end of the power supply. What happens is that if they get bumped the solder connector on the circuit board breaks. If you do not feel comfortable fixing this yourself, you will have to find someone who is capable. Hope this helps.

I had the same problem. You might try the keyboard on good fresh high quality batteries. If this solves the problem, buy another ac power adapter. Good luck!!