HP-97 Charging circuit not working

[rprosperi]

There are at least 2 board designs for the 97 (maybe more) and both are not covered in the original service manual. I don't know if the later design was ever documented in a later revision of the service manual, but take at look at this one (June 1982), it may be different from yours:

https://literature.hpcalc.org/items/1127