So I’m having a bit of a recurring problem with dropped chains (stop giggling Adam pls) when going from big to small ring. It generally happens when I’m shifting down the cassette at the same time, but not always. This is with Campy 10 sp, mix of veloce old and new, record FD. I put the bike together myself, and given that I am an aspiring bike mechanic, there’s lots of things I don’t know. What am I doing wrong? Any tips?
You probably need to adjust the limit screw a little bit so the mech doesnt swing quite as far across. It could be as little as a quarter of turn.
Yeah, I keep on doing that, then undoing it, then doing it again… hard to get it just right. The FD seems to be positioned properly relative to big ring/chain.
If it’s happening while doing a front and rear shift, maybe the rear mech isn’t taking up the slack quick enough. No idea how to fix this if so #almostprobikemechanic
the height of FD is also important. Sometimes you need to have a bit of chain rub for it all to work, but only in gears you shouldn’t be using anyway. Hard to say without seeing it.
Here’s your problem.
I literally starting smiling when I saw the title.
Seriously though, I thought it’s not good practice to shift both derailleurs at the same time. I always just shift the rear first then the front.
I reckon that’s a good point. But yeah, that flies over my head as well.
I’m gonna try that
Thanks for delivering Pinzo. What with HMC making serious comments now 
have you tried turning it off & on?
Could be too much cable tension so when you shift down it’s very violent and drops the chain.
Try Shimano?
Yeah, thought about that also, will try. Downtube barrel adjusters on that bike too, so not too onerous to give it a go.
this will be last serious contribution for some time.
ftfy
haha fml
you’d go great in our IT department 
I work in a museum, and every morning we have to open up the back of a display, pull a plug out and put it back in to get the AV working. There’s even a manual with photos.
On topic: check cage height so it sits a couple of mm above the big ring, make sure the cage is parallel to the chainrings, and crank the limit screw down until it rubs in the lowest gear and then back it off until it just stops.
Do you have short chainstays?
I’ve done all that but will check again. Chainstays are 41/41.5 cm which is fairly normal for an early 90s steel roadie - don’t reckon it’s massively short. But the rear wheel is fairly close to the seat tube, it could go backwards in the dropouts for a touch over a cm.
Campy does not like shifting front and rear at the same time, the only time I have ever dropped a chain is while doing it.