Casio-ctk731| ac-input not working

[Rbrduy_1108]

Dear people of the internet

I've owned this casio keyboard for a while now and it used to be from my father. The pin that is found on the jack in the back of the keyboard was broken off and got stuck in the adapter ac plug. I was hesitant to repair the ac jack but after a few years of paying and playing on batteries i decided to order the same connector and a new adapter to try and fix my keyboard.

After soldering the new one in place and plugging in the adapter which has a specification of 12V, 1.5A and 18W of course it didn't turn on. (It's not because of sloppy soldering) I checked with a multimeter after plugging the adapter in and there seems to be 12V over the ac jack. There also seems to be 12V over the transformer. The diodes give a reading of 0.4V. I have limited electronics knowledge so i won't get any further than this. It's also not because the entire board is fried because the keyboard still works perfectly fine on batteries.

Is there anyone that could help with this problem or any solutions? I'd be happy for a solution that uses the dc connection from the batteries.

I'll leave the schematic for the keyboard below:

Elektrotanya for electronics experts

Electronics forum for electronics experts to repair defective appliance.

elektrotanya.com

And my email if you want to contact me personally:

(e-mail address removed)

 

[delaware dave]

Its a nearly 30 yo keyboard valued today at a $200 replacement cost. Might be better off looking for another one and using the current one for parts replacement.

 

[Rbrduy_1108]

Its a nearly 30 yo keyboard valued today at a $200 replacement cost. Might be better off looking for another one and using the current one for parts replacement.

Thanks for the interesting reply i'll definitely keep this as a last resort. But i really want to try and fix it no matter what. As long as it works and i can't fix it i guess i'll just keep playing on batteries. Thanks for the reply!

 

[Cosmos]

Dear people of the internet

I've owned this casio keyboard for a while now and it used to be from my father. The pin that is found on the jack in the back of the keyboard was broken off and got stuck in the adapter ac plug. I was hesitant to repair the ac jack but after a few years of paying and playing on batteries i decided to order the same connector and a new adapter to try and fix my keyboard.

After soldering the new one in place and plugging in the adapter which has a specification of 12V, 1.5A and 18W of course it didn't turn on. (It's not because of sloppy soldering) I checked with a multimeter after plugging the adapter in and there seems to be 12V over the ac jack. There also seems to be 12V over the transformer. The diodes give a reading of 0.4V. I have limited electronics knowledge so i won't get any further than this. It's also not because the entire board is fried because the keyboard still works perfectly fine on batteries.

Is there anyone that could help with this problem or any solutions? I'd be happy for a solution that uses the dc connection from the batteries.

I'll leave the schematic for the keyboard below:

Elektrotanya for electronics experts

Electronics forum for electronics experts to repair defective appliance.

elektrotanya.com

And my email if you want to contact me personally:

(e-mail address removed)

Your new adapter should have a DC output and not AC take care. The supply coming out should be direct current DC.

The supply input of your keyboard is not AC but DC meaning that one wire is + (plus) the other a - (minus).

Did you take care to the polarity (+ & -) when you soldered the DC plug to the adapter's cable? If you put the polarity wrong the keyboard won't power on. There is a protection diode inside the keyboard for this as else you would blow up the power inside and also possibly the main cpu board.

If you put the polarity right, check this on the plug you soldered with a multi meter set to the 20volts DC range it should read +12v.

Let me know should you be needing further help. I'm a retired technician now.

 

[bwong24]

Not sure it this would work -
1- install 6 rechargeable D-batteries (not sure if NiCad or NiMH is best)
2- wire the jack directly to the batteries
3- plug the adapter to charge for short periods
no charging circuitry, so probably not safe to plug in long periods

If anyone has a better understanding of circuitry, please add comments.

 

[Cosmos]

Not sure it this would work -
1- install 6 rechargeable D-batteries (not sure if NiCad or NiMH is best)
2- wire the jack directly to the batteries
3- plug the adapter to charge for short periods
no charging circuitry, so probably not safe to plug in long periods

If anyone has a better understanding of circuitry, please add comments.

I wouldn't recommend this it is not as things should be for safe practice.

 

[Rbrduy_1108]

Your new adapter should have a DC output and not AC take care. The supply coming out should be direct current DC.

The supply input of your keyboard is not AC but DC meaning that one wire is + (plus) the other a - (minus).

Did you take care to the polarity (+ & -) when you soldered the DC plug to the adapter's cable? If you put the polarity wrong the keyboard won't power on. There is a protection diode inside the keyboard for this as else you would blow up the power inside and also possibly the main cpu board.

If you put the polarity right, check this on the plug you soldered with a multi meter set to the 20volts DC range it should read +12v.

Let me know should you be needing further help. I'm a retired technician now.

Hey, first of all thanks for the reply! I think there's a little confusion i only replaced the dc jack at the back of the panel (see the attachment). The other thing that might cause the problem is the adapter i chose but i'm pretty sure i got the specs right and i seem to be getting a reading of 12V over both the jack and the transformer. As for the polarity i'm pretty sure that's unchanged since i soldered an exact replacement in the same spot. Hopefully that clears some things up!

The adapter i bought:

https://www.amazon.nl/dp/B07HL7NFTF?ref=ppx_yo2ov_dt_b_product_details&th=1&language=en_GB

 

[Cosmos]

Hey, first of all thanks for the reply! I think there's a little confusion i only replaced the dc jack at the back of the panel (see the attachment). The other thing that might cause the problem is the adapter i chose but i'm pretty sure i got the specs right and i seem to be getting a reading of 12V over both the jack and the transformer. As for the polarity i'm pretty sure that's unchanged since i soldered an exact replacement in the same spot. Hopefully that clears some things up!

The adapter i bought:

https://www.amazon.nl/dp/B07HL7NFTF?ref=ppx_yo2ov_dt_b_product_details&th=1&language=en_GB

Yes the output of that adaptor is 12V DC ok. But in the adaptor's specifications there isn't listed if the center pin is negative or positive, so you'll have to check this out. The keyboard has internal (center) pin negative (-) so you have to make sure that the adaptor's plug internal center pin to be negative as well.

Another reason that the keyboard will not power on could be a plug and socket mis-match. Casio usually have a type of non standard supply socket that is a bit rear to find and match. You have to check the continuity with a multi meter whilst the plug is in the socket with the adaptor off. There has to be continuity between the plug and socket.

Let me know should you need further help. Good luck.

 

[happyrat1]

Did you check the diodes with both polarities? If they're shorted internally in both directions then they are toast.

 

[Cosmos]

Ok so i measured the voltage over the adapter and the newly connected dc jack. They seem to be in the configuration where the inner pin is the one recieving the positive side and the inner shell of the dc jack is for the negative side. I've drawn this on a paper for a little bit of clarification. So if you say it's center pin negative then that might be the cause of my problems. Do i just solve this problem by switching the polarity by soldering two cables opposite of the pins? Or should i get an adapter that has a negative pin connection. Or any other solutions? Thanks already for everyone's help and support!

The drawing i made is attached below

Yes you need to 'reverse' the polarity so that the center pin is - negative. Like I mentioned before almost all Casio's use a - negative center pin. Also I'm assuming that the DC supply socket (it's not called a jack) you fitted in the keyboard is an exact match of the old broken one, chances are it is.

So at this point you don't need to do anything more to the keyboard. But you need to reverse the polarity of the DC supply plug of the adaptor. So long as it doesn't have a polarity switch that you can switch polarity, I'm assuming no.

If you can open the adaptor (with screws) you can de-solder both wires of the DC supply output and reverse them. If the adaptor is 'sealed' just cut the DC supply wire and reverse both wires then use some tape or otherwise to insulate them.

Hope that helps for your treasured late father's keyboard.

 

[Rbrduy_1108]

Yes you need to 'reverse' the polarity so that the center pin is - negative. Like I mentioned before almost all Casio's use a - negative center pin. Also I'm assuming that the DC supply socket (it's not called a jack) you fitted in the keyboard is an exact match of the old broken one, chances are it is.

So at this point you don't need to do anything more to the keyboard. But you need to reverse the polarity of the DC supply plug of the adaptor. So long as it doesn't have a polarity switch that you can switch polarity, I'm assuming no.

If you can open the adaptor (with screws) you can de-solder both wires of the DC supply output and reverse them. If the adaptor is 'sealed' just cut the DC supply wire and reverse both wires then use some tape or otherwise to insulate them.

Hope that helps for your treasured late father's keyboard.

1,000,000,000 points to Mr.Cosmos!!! The problem is solved! I had an old universal adapter laying around which i used to match the reverse polarity. This was indeed the problem. How exhilarating! It was truly fun repairing and solving this problem alongside you. I also felt like i learned a lot from this so thanks for helping me fix my dad's keyboard!!

 

[Cosmos]

1,000,000,000 points to Mr.Cosmos!!! The problem is solved! I had an old universal adapter laying around which i used to match the reverse polarity. This was indeed the problem. How exhilarating! It was truly fun repairing and solving this problem alongside you. I also felt like i learned a lot from this so thanks for helping me fix my dad's keyboard!!

Glad you finally solved it. I've spent many years working on Casio and lots of other brand keyboards