SR-52 Feed Motor Noise

[NeXT]

I rebuilt the battery pack for my SR-52 programmable calculator and while the roller is getting soft, it will still pull cards through and it won't mark them up.
Problem is the geared motor in this thing screams like it has a dry gear or bearing inside and I can't see any way to get a drop of oil into it. Is it just non-serviceable?

 

[Leviset]

I was recently given an SR-52. It has its original battery pack (40+ years), still recharges and holds its charge!