old SANWA radio with no trainer socket

[bitmaniac]

Hello everyone!
I own a (rather old) Sanwa Space PCM 6ch radio.
Although IT IS a PCM it doesn't supports a training
plug or digital output.

After getting your valuable infos on some other radios
modification I wonder if it would be possible to add
this support to my Sanwa PCM -a digital output could
be a good idea!.
Can you give me some advice in wich section of the
circuit should I search or pay attention???

THANKS ,
ALEXANDER - GREECE