Vintage Synth Repair

Hello all, Im a newb here and have re-ignited my long since dormant love of synths & electronics, so finding this group is great! Id like to buy a faulty JX3P from ebay and need some advice on the problem & see if anyone can advise.

The fault is that only the first bank (bank A) of preset sound buttons work - it is not possible to select the second bank of preset buttons (bank B) or the bank of buttons (bank C/D) that control the various functions of the sound editor/mapper.

Should I purchase & indulge? I would say my knowledge is intermediate and I do not have a scope now as I sold it years ago, maybe time to get another one? .. are those cheap nano scopes any good?

Any info would be great.

Best regards & thanks,
Nick