I acquired a 3799 ceramic Top Gun doppel many months back. It has been sent back multiple time for repairs for a particular problem with the chronograph. As you know the 3799 has the IWC caliber 79230 which is based on the 7750. I have noticed that each time the chronograph is engaged for a couple of hours and I stop it intermittently, the chrono hour hand tends to overshoot the sub-dial marking for the correct hour. This becomes a particular problem when the chrono is run for around 10 hours or so with my having stopped the chrono a couple of times in between - the chrono hour indicator can be misaligned by almost half an hour!
Interestingly, the hour hand is perfectly aligned when the chrono is reset, or when I don't stop the chronograph in between - in such a scenario, it always matches up with the correct sub-dial marker after the elapsed number of hours!
When I first sent the watch to IWC, I was told that there was some grease related issue for the chrono hour hand. I noticed the same problem when they returned it. This time when I sent it back, they said the entire chronograph gear train will be replace. I got back my watch yesterday, and the problem still seems to be there! ARRRRGH!!!
I have attached a picture I took today...
I ran the chronograph for 4 hours to test whet the problem had been fixed, with intermittent stops in between. After four hours have elapsed, you can notice that the chrono hour hand has off-shot the 4 o'clock marker on the sub dial!!
I am almost on the verge of giving up! Is this a common issue with valjoux 7750 based movements? Should I just live with it, this being one of my grail watches?
Any advise appreciated!!!