Hi All. I had a Roland KR-3500 Digital Piano (similar to the KR-4500) that exhibited a Crackling audio sound on all keys. After reading somewhere about someone with a similar issue who had replaced all the Electrolytic caps I decided to also go down that route. (Spoiler : It worked !) After some basic troubleshooting I determined that it could be noise feeding thru from the Keyboard scanning since the Demo tunes played back undistorted and the Audio amp / speakers were fine ( Inserted an Audio signal into the rear Audio input). After extracting the main board from the shield, I replaced 7 Capacitors that ,although not looking damaged or bulging ,showed signs of leaking on the PCB area around them. I also repaired a damaged feed-thru and cleaned the board. After re-installing the board I checked that the issue was still there. I replaced a further 16 capacitors and finally the Audio was normal. There remain about 20 caps that I did not replace (and will probably have to in the future...but I'm not set up with proper fume extraction and the Solder fumes were getting to me so I decided to stop ;-) After measuring the removed components it was a wonder that the Keyboard worked at all ! All the 10 uf caps read under .1 uf ...I began to wonder if I had damaged then during my de-soldering, but after doing a test solder/de-solder operation on a scrap board I realized that they were really ALL BAD. In my case it was the 3.3uf caps that created this audio distortion ( C11,14,15,18,22,29,24 & 31) But the bottom line is I would suggest just replace all Electrolytes on that board ( Main Board Assy 7627590000 in my case). ( Qty. 19 10uf/16v, Qty. 4 10uf/25v, Qty. 8 3.3uf/50v note: I used 4.7uf to replace these 8 with no adverse effects) Hope this helps someone. P.S. to open the piano there are 6 screws, 3 on each side underneath that once removed allow the top to be lifted like a car hood. Also there is a troubleshooting mode that can be accessed by pressing "Advance/Basic" and "Sync Stop" buttons while turning on the unit. Select the 14 tests with the "inc" and "dec" keys.