Ensoniq KT 76 distorted output

Hi,
I got in Ensoniq KT 76. The right, left, and headphones outputs are distorted. I thought I would fist do a factory reset but I can’t figure out how.
Thanks

PRESS EDIT/SEQUENCES (PRESETS). PRESS AND HOLD THE UPPER 9 BUTTON AND THEN PRESS THE LOWER 9.RELEASE BOTH AND PRESS YES AT THE PROMPT.

extracted from here:
http://www.dlse.nl/synthrepair/reset.html