Actually, you can turn off the internal speakers by merely inserting a 1/4-inch dummy plug into the headphone jack, which is how I used to play my S-950 for more than a decade. Mine lasted through thousands of music jobs, performed flawlessly 7 days a week, 365 days a year and often, up to 3 jobs a day. I recently blew an internal speaker, which is rare, but replaced it and everything still works just a great as the very first day it came out of the box. It is a workhorse keyboard, and I absolutely love all of the wonderful features.
Now, I have access to a repair guy who can often replace individual parts on a board without replacing the entire PC board. He is located in Southern Pennsylvania. If you wish to have his contact information, you can PM me and I will be more than happy to provide it for you. Additionally, he makes house calls for pro musicians who reside a reasonable distance from his home.
Good luck,
Gary