//c screen output gone wrong

[cordsanne@aol.com (CordSAnne)]

My Apple //c recently moved, and now I have set it up in its new home,
it's misbehaving.  When I switch it on, instead of coming up wwith "Apple
//c", the screen goes covered in 8x8 blocks of } alternating with inverse
@, (a bit like the initial screen display on a ][+) and garbled text
characters spread accross the screen.  If loading a 40char/line program,
that's as far as it goes, but if loading an 80 char/line program eg
appleworks, the correct screen display comes up but  with every other
character printed twice eg "Exit?" would show as "EEii??" or "xxtt".  The
disk drive makes all the right noises, the characters on the monitor are
the right size/shape etc.  The monitor is an old green on black one from
our old ][+ of many years ago, and runs off the monitor output of the //c.
 Oh and just in case it helps, when I recently typed "print peek (64447)"
as suggested to someone else on this group recently, the answer was "0".

So what's wrong with it?? It  seems to me that it's in the interface
between the thinking part and the display part (if you see what I mean). 
Any ideas??

thanks for any help,

Bod