Afternoon Gents, Recently purchased new a Seamaster caliber 2500. Wound, set date and time to an atomic reference. Wore it continuous for a week. Checked accuracy daily. Was approximately .5 seconds fast and I was extremely pleased. Removed from my wrist and set it on my dresser with caseback down, put it back on my wrist about 24 hours later and gave it a wind. No magnetic devices near, although while wearing, I’m using a cellphone or iPad or computer like the rest of us. The accuracy is now minus 15 sec a day. I own “less” quality automatic timepieces with standard ETA movements that are under the same conditions that keep consistent time. Any thought would be appreciated!
That sounds really strange, i would run a compass by it just to confirm that it was not magnetized somehow. When you wore it continuously for a week, you also left it on your dresser with the caseback down every night?
We may have to wait on some more knowledgeable members to chime in but my understanding is that when a watch is on your wrist it averages out how accurate the watch is in all different positions. When watches are measured they are measured across 5 or so positions to get the average change. I admit it seems unlikely but it is possible that your watch is not very accurate when the caseback is down, it may be helpful to see how our watch is when you leave it with the crown down for a night to see how it changes. It just seems strange because if you bought the watch new, it was tested by Omega in multiple positions, including with the caseback down. Outside of magnetization or being dropped, I am not sure what could have caused such a drastic change.
Strange for sure. Watch was never dropped and a compass is not indicating magnatism. Thanks for your input. We’ll see if anyone has further ideas.
Greetings. I may not able to answer the issue because I am not a knowledgeable watchmaker and I am just an ordinary person who wearing watch everyday. However, I may able to share the experience about accuracy with you. Now it is already 2 years since I bought my first Omega which is Speedmaster Day-Date Ref. 3520.50 equipped with Omega Cal.1151. My first year the watch is quite fast and it is about +5 seconds per day. Now it is 2 years past and, due to the summer time in Thailand right now, my watch is -4 to -5 seconds per day. Still, I am very please with the performance. In your case, if I were you, I am definitely anxiety and worry about the -15 seconds per day for sure just like you.
That would be the magnet inside the compass...something that many people seem to miss. Using a compass is pretty much a waste of time - just demagnetize the watch if you think it needs it.
If you are winding the watch before putting it on, wearing it for days and it's losing this much time, I would suggest using the warranty. Timekeeping should be between -1 and +6 seconds per day average rate. Cheers, Al
Thanks for the comments and suggestions. I’m going to start from the beginning as if I just received the watch.
from wiki: Segal's law is an adage that states: "A man with a watch knows what time it is. A man with two watches is never sure." My PO 2500 is 8 years old and not yet serviced, SM300 is 53 years old and serviced recently. 20th February SM looks to be 1 min 17 seconds ahead by 28th February looks to be 41 seconds ahead 36 second change in 8 days, 4.5 seconds per day but tells me NOTHING.
Could it be due to positional variation from daily wear vs positional variation from sitting in a fixed position?
So for the 2500 the average daily rate should be between -1 and +6, but as you note not every position will fall within that range. The max. allowed Delta (positional variation measured over 5 positions) is 12 seconds at full wind, and 15 seconds at 24 hours after full wind. Looking at the numbers if the watch has one position that is -15, and the average rate is even at the minimum -1 second per day, then the other positions would have to be a lot faster in order to get that average - it would fail on overall Delta. To stay even within the 15 second number for the Delta if one position is -15, then the fastest all the others can be is zero. If the OP's numbers are right, this watch is almost certainly out of spec in one way or another.
Gentlemen. Again, thanks for all your input on this subject. Before sending the watch for warranty service, I brought it to my watchmaker. Watch was HIGHLY magnetic. He demagnetized it, and scoped. Watch is back to normal spec time keeping. He was definitely puzzled as to why it ran slow. Stranger things have happened. Regards.
In most cases the watch will run fast when magnetized, but I've seen watches slow down and some stop because they were so highly magnetized. The rule is there is no rule... Cheers, Al