So I'm dealling with an old ETA 2783 (In case some of you did not fiddle with this particular model, it's basically a 21600 version of 2824) . Normally I can get a 280 amplitude with this model but this time I have a lot of trouble. What I get now is 240~250 and +4s/day Dial Down/Up, 200 -15s/day Crown Down/Up. I've check the endshakes and the hairspring seems fine to me. Anything else should I look for. What's your intuition if you face such problem? Thank you guys!