how to identify old ic's [ sony ] ???

[Peter Blackett]

HI ,
I'm asking this on the synth diy list as I know someone here may have
kept some  old sony data books around.Anyone  know of an a to d
convertor marked
 5C002

I'm trying to help a friend repair their synth and find out more info
about this ic .
I've tried http://www.icmaster.com/
that has free registration , but doesn't find anything 
and also http://www.freetradezone.com/
or even http://www.questlink.com/

but no luck .

according to what info I can find out , there are two versions of the
machine involved [ a PPG waveterm ] and I've only managed to find the
service info for the other version.

any suggestions ?
regards Peter 
South London England