Broken HP 71B. Where to start?

[Seirin-Blu]

Hello,

I'm very new to the world of vintage calculators and come from the land of vintage mechanical keyboards. I recently found a broken HP 71B and am a little bit puzzled on where to start. I cleaned the corrosion off of the battery contacts and opened it up to see if there were any exploded capacitors (there weren't). There seems to be a bit of corrosion on the band between what I assume is the motherboard and display/keypad that I cannot seemed to clean of without damaging the cable. Is there something I can short to turn it on from the motherboard and check? Or should I just list this on ebay to someone who knows what they're doing more than I?