Repairing a CR-78

This is a post that's been in my backlog for a while, because I knew it would take some time to write it...

Back in February this year (2013) I got a request from someone if I could repair a CR-78 with severe battery leakage. A repair-shop that was asked about it wouldn't do it because it would take too long and not be worth the time/money.
Well... I'm cheap, but I leave no guarantees that I'll fix it 100% or that I'll do it quickly, but I'll do my best. That was good enough for this guy, so he let me have a go at it.
The actual "practical" symptoms weren't actually that bad though:  Not possible to save rhythms

However, considering the massive leak, it was clear that this machine needed more than just a quick repair.
No way should anybody give up on a such a fine machine unless it's totally hopeless.
Challenge accepted!