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HELP KAWAI MR240 sound issue
#3029118 09/25/20 11:01 PM
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Ok, so I got this old KAWAI MR240 that belonged to my aunt, I realize how old it is, but still I would try to make it work.

It used to work fine, until one day after a few day turned of, when I turned it on again the piano started emitting a loud noise through the speakers and the output jack.
It makes no difference which piano voice I choose, it makes no difference if I press any keys, the leds from the menus they light up, but the noise coming out is the same.
I took to two different technicians here but they couldn't help me.

I believe some experts in piano might know what it is. I just need a diagnostic. Anybody knows what it could be? Maybe a faulty component? What would cause this kind of problem?

I am desperate I've looked everywhere.

there's a video of the problem in this link
https://youtu.be/CBmWozdSvwA

If anybody encountered a similar issue in another digital piano, another brand even, and they managed to diagnose and get it fixed, please can you help me?

Re: HELP KAWAI MR240 sound issue
Danielares #3029156 09/26/20 04:04 AM
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What's your skill level in electronics? If zero or low you're onto a loser here. A hobbyist might help but lack of parts availability might also be a problem. Have you opened it up? Some initial things are sometimes obvious, blown or leaky caps, burnt tracks, signs or heat, visible dry joints. I would do that but probably not spend more than 10 mins on it if nothing obvious.

Re: HELP KAWAI MR240 sound issue
spanishbuddha #3030123 09/29/20 03:24 AM
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yeah I took a look at it, I usually fix everything I set my mind to it, but this one is beyond my skills. I can't even identify where the problem is. That's why I wanted to see if someone had a similar problem.

Re: HELP KAWAI MR240 sound issue
Danielares #3030132 09/29/20 04:41 AM
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Start by the power supply. Inspect electrolytic capacitors, see if there are any bulging. Disconnect and reconnect connectors, that could help to determine if there are bad contacts. Those would be my first troubleshooting steps. They, trying to find the service manual in the internet and measuring voltages with a multimeter.


Kawai ES8, Roland RD2000, Yamaha AG06 mixer, Presonus Eris E5 monitors, Sennheiser HD598SR phones.
Re: HELP KAWAI MR240 sound issue
Danielares #3030137 09/29/20 05:08 AM
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That sounds like a ground loop to me. probably caused by the power supply.
First troubleshooting step for me would be to try connecting to different power socket in a different room first while unplugging all other electronic devices that share the same power line. Maybe you ll get lucky.

I am not sure if that Kawai has balanced outputs. If it does, you can buy a soundcard with balanced inputs and outputs and some balanced cables from Amazon. You can return them back for a refund if it doesn't work.

You can also try buying a DI Box from Amazon and return back for refund if it doesn't work.

But look at this link to identify if this is your issue:
https://speakerchampion.com/fix-pa-speaker-problems/#:~:text=Basically%2C%20ground%20loop%20is%20an,a%20buzzing%20or%20humming%20sound.

Last edited by karoloydi; 09/29/20 05:16 AM.
Re: HELP KAWAI MR240 sound issue
Danielares #3030777 10/01/20 01:56 AM
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Thank you all for the suggestions I'll try them out and post here the results!

Re: HELP KAWAI MR240 sound issue
Danielares #3030839 10/01/20 06:54 AM
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This is certainly not a ground loop. The piano is not connected to other equipment.

This is likely a power supply issue. It's odd that two technicians could not offer help.

But there's little choice. Find a proper tech. (Or find a new piano.)

Re: HELP KAWAI MR240 sound issue
EVC2017 #3032394 10/05/20 05:20 PM
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Originally Posted by EVC2017
Start by the power supply. Inspect electrolytic capacitors, see if there are any bulging. Disconnect and reconnect connectors, that could help to determine if there are bad contacts. Those would be my first troubleshooting steps. They, trying to find the service manual in the internet and measuring voltages with a multimeter.

Electrolytic caps get old... I took a look to those on the power supply and/or amplier (you can identify this zone of the board by the heatsink)


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Re: HELP KAWAI MR240 sound issue
Marcos Daniel #3033504 10/08/20 06:14 PM
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Thanks! I'll take a good look at that


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