Dead Longacre Scales. Repair options?

Have some wired scales that worked, were put in storage with the AA batteries still installed, and the batteries corroded/exploded, but any corrosive stuff seemed to be contained to the battery box. Control board looks clean. No corrosion or obviously burnt things. I bought a new battery box and connector from Digikey after an over-the-phone quote for replacing the battery box was given as "usually $300 or so". I got the new box and connector for $15 (thanks to help from GRM on type of connector and where to buy).

I've verified it's putting out 9v on the connector, but still no life in the scales. Any tips on a next step before what seems like an expensive trip for repair on old-ish scales (may or may not be worthwhile).

Thanks!

maybe a silly question but are there other batteries somewhere else too (like a watch battery somewhere on the board)? Is the polarity correct on the connector?

There are no silly questions!

Polarity is correct unless I'm just totally spaced out on Red/+, Black/-. Not aware of any other batteries.