Ensoniq tech available
While this thread is 3 years old, I did stumble across it Google'ing for something else related to Ensoniq. Since some of us really love our Ensoniq's, I'm replying.
One repair technician in San Jose, CA used to work at Ensoniq/EMU before it closed down. He bought many of the remaining parts. He services and sells Ensoniq products. (I bought an upgrade kit to convert KT-76 to E-Prime.)
He may have a replacement board for your SQ-1 or offer you ideas if he can fix it.
His web site goes by the name Thesoniq.com
(Since this is my 1st post, I can't post URL's yet. Just Google Thesoniq.)
(408) 259-6193