I'm in danger of becoming a Campag convert! This overhaul job was easy and very satisfying. I'd been warned by most that three hands are required for this job, but if I'd had a bench vise, I could have done it with one hand. Don't listen to the hype, Campag owners, this is straightforward.
The nominally difficult (but really easy) part is retensioning the main flat spring at the back of the shifter, after you have stripped it down, replaced your broken part, and reassembled the cleaned parts with fresh grease. Simply place the flat spring in the slot on the axle, hook the end on the shifter body (for a pre-'98 shifter) or the spring carrier (for a newer shifter), place your hex key (for a pre-'98 shifter, or your large flat-blade screwdriver for a newer shifter) in the socket on the axle and turn the axle (clockwise for a left shifter) until it drops down ~ 1 mm into the slot on the other half of the axle. Now, provided that you are careful, you can remove your hey key (or screwdriver) and let go: the spring tension keeps everything in place - no need for three hands! It may feel a little more secure if you press down on the axle with a small tool as you pull out the hex key. At your leisure, drop on the big disc washer and screw in the retaining bolt.
The shifter now feels like I have changed from Mirage to Super Record. (Conversely, I wonder how many people are riding Super Record that feels like Mirage because they haven't cleaned the innards lately?) I suspect that the feel of the shifter depends a lot more on its state of maintenance than on which model you have.
Thanks very much, Peter, your diagnosis was spot on - the long arm of the thumb-lever return "banjo" spring had broken off and was loose inside the shifter. Thanks also for your prompt service. The original index springs looked fine, so I cleaned them up and left the new ones for later.
Differences between old and new Campag? Minimal indeed. I used a Campag video for '08 Record to take me through the overhaul process for my pre-'98 Veloce - it was invaluable. The new Record had a ring washer between the spring carrier and the cable spool/ratchet body that the old Veloce doesn't have, and the new Record spring carrier, apart from being composite, has a post for the main flat spring that is lacking from the old metal Veloce spring carrier. Apart from these, there were no differences at all. (I didn't strip down the components in front of the spring carrier, so I can't comment on differences there.)