Have had a similar problem with the same machine (25 years old I have to admit), and just mended it today.
Opened from the underside (2 screws), after pushing the tilting button. Saw a burned resistor after a while with a remaining green band (it means number 5 following the color code).
Tried first to replace it with a 560kohms resistor, with no result, then with a 56kohms, and hey presto, it worked.
Cost : 0,1 € and 8 hours work (a lot of cleaning).
alain.deffrennes, November 2007