Originally Posted by
TurbineBlade
+1. With friction shifters (like your FD downtube shifter) you probably just have the cable too slack when the shift is let all the way out.
You can leave it like that so long as your shifter is still able to move enough to shift your FD to the high limit -- I don't know why your cable broke. That's a separate issue.
The slack should be removed with the shift lever all the way forward and the front derailleur in the small(est) chainring as RG recommended. If you have too much slack when the lever is forward, it's quite possible for the cable to slip sideways off of the shifter's "drum" when you go to upshift to the large chainring.