Good idea to keep an eye on the repairer, however reputable they might be. They may think "replace with a lesser specification transformer rather than have a re-wind on the Partridge, just to repair it quicker and therefore 'please' you"...
The P.M. ( we may as wll do it here )
was about just what string types/gauges and picks you use. As a fellow S.G. user, but with a different playing style/tone, it's Stormy Monday's and D'addario 10-52 with a BKP 1.21 celluloid pick.
I therefore curious what works for you and your Riff-Raffs/playing style.
In guitar magazine interviews, Angus seems to be using EB 9-42 and a heavy pick, but on guitargeek.com they say he uses 10-48 !
FF.