Shorted is not the condition causing the fault.

You need something to test ESR and capacitance ...

The other option is if your not interested in troubleshooting, you can replace the one's you haven't replaced. If you are interested in troubleshooting the problem, you'll need more than the meter.

You can get a multifunction tester ... not a professional one, for really cheap that can give you some indications of out of specifications.

From the problem description you have, it would be better if you had some type of oscilloscope and something to check the ESR and value of the capacitance.

What part of the world are you located?

 

I see thanks

 

It might be a cap that's failing (high ESR and/or lower capacitance) on the power supply. You can troubleshoot by putting a good cap across any caps that you suspect. Make sure you don't short anything. I'd use a couple test clips.

If you do this, check the voltage rating on the suspect cap so you have an idea of the voltages you're working with. It goes without saying that the good cap should have the same or higher voltage rating. Also don't make it huge compared to the original.

By across existing caps, you mean in parallel?

 

yes he means in parallel.

If they are all connected to ground, and from what I saw of the schematic, they are. you can connect the negative to ground and just touch the positive side of the capacitors with the non-grounded lead while you have the noise to see which one reduces it.

 

Thanks for all the suggestions. I replaced C216, C217 and C112, then my piano is working fine. However, after I power cycle, there is loud static noise from two speakers. Key still make sound. No sure if a new part is broken or I accidentally touches something. Please help!

Moderator edit: New thread created from:
https://forum.allaboutcircuits.com/...-95-sound-problem-speakers-headphones.140229/

Hi,

It's been a long time since this post was created, but I hope my experience can still help the original poster and people who encounter the same issue in the future.

After replacing C216, C217 and C112, I run into the exact issue of this loud static noise coming from the two speakers and the loud 'bang' when the piano was turned off. I later found out C112 was the culprit. When I was replacing C112, I damaged the board, and therefore, the continuity test failed between one of the C112's end and its supposed connected point of another component. The problem was solved after I directly solder a jumper wire between these two points to manually construct a connection. Please see the attached images for the exact locations of this jumper wire and the two points.