Technics K700 Keyboard

[rich03]

Im hoping someone here can help me out, I was passed down a Technics K700 keyboard by my grandfather, it started giving trouble a few years back and i simply packed it away after about 4 years of collecting dust and my being reluctant to just scrap it i decided to open it up and attempt a repair i found a few corroded tracks on the pcb fixed them up and it was back to life like new.

Then all of a sudden it decided to start a new weird problem...
it powers up and i can play the preset backing rythms all day long however if i play exactly 8 notes on the keyboard it freezes up after the 8th one, i thought it must be memory related problem as its allowing only 8 bits and maybe not clearing the memory/latch ive been going over the pcb looking for more bad tracks but still not found another, could someone maybe tell me which section of the circuit i should be looking at, i bought the schematics off a manuals site so im not flying blind here.

Thanks