Hi, Visit a site like Norman Leete's
http://members.aol.com/tronpage/maintain.htm and see his Mellotron-
Routine Maintenance, which is like looking at the 400's Owner's
Manual (with Norman's words of wisdom added in).
I have a
Geneva VR205 290 gauss field intensity demagnetizer. It's made in
USA. I got mine from markertek.com for about $ 59.95 U.S.dollars.
Hope this info helps, George Summers Houston, Texas USA
old M400S s/n 553 with me now for 29 years