I had the pleasure a few months ago to work on a Hammond C3 organ and PR 40 speaker cab for a local church here in Sauchie, Alloa, (hey ShadowChancer, you out there?) Thankfully the repair was just to the power/line input to the speaker cab and not the C3 itself. There was a lot of crackling and loud pops when anyone played the keyboard but it turned out that an over-zealous cleaner had moved the cab to clean behind it and in the process had pulled the cable to the input causing it to break and short out intermittently. The repair itself isn't the best you will ever see but done the job and finding a new unit to replace the old one wasn't going to be easy/cheap. Lovely sounding organ, especially when you hear it in situ in the church, got a wee video but it doesn't do it justice. Photos of C3 below, speaker cab (inc necklace reverb unit) in next post.