I wanted a digital piano for a long time , but I also knew - it that was not going to be used more than five times a year ... so the money was not worth it.

I got myself a broken Kawai CL35 and I will be very happy to repair it.

The piano is turning on , but there is no sound from the keyboard.
When turned on I can start the metronome , but if I touch the keyboard (any key) , the metronome stops and can't be started again. Same is the case with the Concert magic and lesson - melody is starting to play , but in the moment I press any key - the melody stops and the only way to start it again is to restart the piano from the on/off button.

Step 1
Press and hold the METRONOME button, then select the desired time signature by pressing one of the
lowermost black keys assigned to that beat.

When I try to this - works, metronome is adjusted nicely with the black keys.


The piano has not been used at all or very little , I can see a quality control label from 2008.
I looked for any bad looking caps , actually I have Fluke that can measure caps , so all of them read in the range they need to be .
Checked for anything that you can see with a naked eye on the boards ... they look like new.
Checked the cable from the CPU board to the keyboard , there is 3.1v and 5v on all the wires to the keyboard when connected.
When pressing the keys and measuring the 5v , can see a small voltage drop to 4.8v , which makes me think that they keyboard is okay , but the signal from the keyboard to the board or something with the signal is bad.

If you have any ideas for further troubleshooting , please share them here Thanks

 

The first step in repairing a device is locating the problem, and in this case we need wore assistance. Does the metronome sound use the same speaker as the music? Is there an earphone connection available? Is there a volume control pedal? I have seen devices with failed loudspeakers, failed volume controls, and failed audio amplifiers. Very seldom will you spot a failed part because it has burned up, and usually when a part burns up it is because some other part has failed. And it may also be that there is some function to mute the audio that simply needs to be switched off.
So if you can obtain either the instruction book or a circuit diagram then a lot more useful advice can be provided. Otherwise you will only be getting guesses.

 

Hi , yes the metronome sound is form the same speaker as the music.
There is a earphone connection , but is the big size one and I don't have a adapter , so will need to order one (no shop around me). I did some more testing and to me , looks like the CPU board is drawing too much power , do you think this is normal ?
When connected to 5V directly to the CPU board (all the cables are disconnected) draw is 0.34A @ 5V .

I took a video of the piano as well :

 

Actually, 340 mA is a reasonable current for a processor board. But without any cables connected it is not a valid test at all. And are you certain that the logic runs on 5 volts, and not on 3.3 volts?
What test equipment do you have available? And do you have any circuit information about the piano? Finding a failure in a piece of equipment with neither circuit information nor test equipment is an exercise in courting good luck! At that point you may have better luck with signal injection, moving from the output amplifier, which might be OK, back towards the tones generator, until you find the place where the signal does not get through. But this method is not as easy as it sounds.
So let us know what resources you can have available. A circuit drawing would be very helpful.

 

Okay, I did not know that this is normal current, also cpu is getting warmer without anything been pluged in.
There is no difference in the draw with or without any cables connected.
I have a service manual for model CL25 (in CL35 , there is 3 pedals instead of 1 , some melodies and a few more sounds ), it's using the same CPU and the board looks very similar. When the power is connected to the normal connector , the voltage is also 5V , it says 5V in the service manual as well.

I have a bench power supply and a few multimeters(fluke 177 and 116),air soldering station, normal solder iron,ect. I don't have oscilloscope.
I have repaired a few laptops, mainly dodgy repairs - I have no experience with schematics.

https://elektrotanya.com/kawai_cl25_digital_piano.pdf/download.html

 

Schematic drawings are the detailed roadmaps of electrical systems, and properly drawn they provide a way to understand what a circuit does and how it does it. So reading schematics is almost as important as reading words, to work with electrical systems. So if you have a service manual with circuits and some means to share the circuits, it should be possible to find the problem on that electronic piano. I repaired an appliance in Thailand from Michigan, USA, that way. It saved a missionary quite a bit of money.