Hello Peter,
Although l haven't used him as l'm a Melburian, Trevor Wilson at Rage Audio in the Sydney Area is the guy you need. He's very experienced and adept with high end audio repair and modificathions. Here is some info and his contact details.....
http://development3.aspac-consulting...%2040%20years.
http://http://development3.aspac-consulting.com.au/contact_us.htm
Best
JA