Help for an old Apple ][ clone

[txt <txt@txt.it>]

Hi,

I have a problem with an old Asem AM64e an italian Aplle II clone. 
Unfortunately today turning it on I discovered a problem on the screen. 
In particular the computer is regularly working, but there are vertical 
sector of the screen which does not display. This both for graphics and 
text. For example in text mode only half of each character is displayed.

I tried to swap between them the ram chip and to reseat all the other 
ICs, but nothing is changed.

Any idea about the cause of this problem?

Thank you in advance

txt