please contact Schaltungsdienst Lange in Berlin
They have all documentation you need for the 320 and
almost every other recorder ever made.
Their charges are reasonable, and their photocopies of
service manuals are immaculate!
I have used Lange from Germany and from Scotland for over 20 years!
Their contact address is:
Schaltungsdienst Lange o.H.G.
Zehrensdorfer Str. 11
12277 Berlin
Tel.: ++49 (0)30 / 723 81-3
Fax: ++49 (0)30 / 723 81-500
They have a good website which you can browse in english!
Good Luck!
James Doyle, MA, Greven, Germany, May 2008