Vintage Synth Repair

hi
has anyone ever added a osc sync input to either a sh101, mc202 or 
cmu810? is it simply a matter of removing the capacitor at pin 9 of the 
cem3340 and adding a jack socket or do you have to add any additional 
circuitry? i am also considering modding one of these to make it 
patchable to use with a modular system or to patch to each other, i 
have seen the novamod designs but have also read it has errors, any 
sugestions or ideas are welcome.

thanks

Stuart