Yamaha Clavinova CLP-150 static and popping from speakers

[samuel phillips]

Hi guys been trying to find the problem on this one but to avail i need help before my brain gets toasted. so to run down is all the voltage test are ok. i found some bad cap i replaced them. So the owner told me that a few months ago they turned it on and heard the same static and popping sound, they would leave it on for a bit and then the static and popping would die down.

Then the piano would work like normal, they ran so for a while, until now that is all you get static and popping from the speakers. i tried running the test program and it freezes. On a cold start up the lcd freezes and no functions work sometimes on start up the lcd is blank but after while of staying on you get functions but no sound from keys only the static and popping. I know this instrument is old but i would like to help them get it up and running again. i'm all ears as to what could be the issue here. Here is a link for the service manual.
(http://mharding.net/wp-content/uploads/2017/01/yamaha_clp-150.pdf)

 

[Harald Kapp]

Start by measuring the supply voltages (on the low volt side). Do you have an oscilloscope to look for excessive noise on the power supply rails? When changing capacitors you may well have overlooked one or the other defective one. Not all capacitors fail visibly. Since it is an old instrument, chances are that the electrolytic capcitors simply dried out with time which will lead to excessive ripple and noise on the power supply lines.

 

[samuel phillips]

Start by measuring the supply voltages (on the low volt side). Do you have an oscilloscope to look for excessive noise on the power supply rails? When changing capacitors you may well have overlooked one or the other defective one. Not all capacitors fail visibly. Since it is an old instrument, chances are that the electrolytic capacitors simply dried out with time which will lead to excessive ripple and noise on the power supply lines.

All voltages are fine, I will change all the caps and let you know what happens thanks.

 

[samuel phillips]

Start by measuring the supply voltages (on the low volt side). Do you have an oscilloscope to look for excessive noise on the power supply rails? When changing capacitors you may well have overlooked one or the other defective one. Not all capacitors fail visibly. Since it is an old instrument, chances are that the electrolytic capacitors simply dried out with time which will lead to excessive ripple and noise on the power supply lines.

@Harald Kapp good news bad news. Good news is that changing the all the caps solved the issue with the sound piano now a new problem has arise the lcd screen has no display. On reinstalling the board after the cap replacement on first boot the screen worked but the speaker won't turning on checking that the +12 regulator decided to die so i replaced it when i turned back on the piano works well but no display after a few turn on and turn off doing some test for voltages the screen part showed data like patches certain parts blank i'm still learning electronics so i'm lost. From testing ic9 and ic 10 are getting voltage and on the connector for the lcd screen has the correct voltage also i forgot to mention that the screen light is working too just nothing displayed.

just some other info i did not change 3 caps 1 @4.7uf which tested ok and 2 which i didn't have the value they were close to cpu quartz crystal around that are c151 and c245.
any advice as to what could be the cause it was working good before i changed the regulator.

 

[Harald Kapp]

Check all connectors to the display for correct fit and secure fastening.

 

[samuel phillips]

Check all connectors to the display for correct fit and secure fastening.

I did that even took out the area where he screen is, clean and reinsert the flex cable.