Welcome to the SE club
I have 2 of them a 800k one that works but the analog board might be bad but i'm not sure about that
And a nice SE SuperDrive that works well
https://androda.work/product/powerbook-passive-matrix-display-flex-cable-replacement-140-series/
I would try getting those I bought one for my PowerBook 145 that also had a broken flex cable for it's LCD