Cal 550 Power Reserve Issue

O OldCMS

I have a 1962 Seamaster 14797, Cal 550, that I'm bringing back to life after sitting in my dresser for approximately 7 yrs. From my research the power reserve should be 38 hours but yesterday after taking it off my winder and wearing it around the house, it did not run through the night. I took it off around 1100 pm and it stopped around 545 am. It appears to be keeping pretty accurate time - gained about a minute of 5 days on the winder.

Could or would this be a weak mainspring issue or would it just in need of a general servicing?

I'm not trying to be a watchmaker, but I'd like to be a little smarter before I take it to my local Omega-certified repair guy.

Thanks in advance for any thoughts or ideas.

Out of TIME!

FYI The pror comments noted.
Wind the watch manually.
Check run time after a manual wind.
Automatic watches have a bridal that slips on the inside of the barrel.
The mainspring bridal maybe slipping before a full wind.
The mainspring maybe broken & slipping.
Or as noted prior auto wind not functioning.
There is a special lube for auto mainspring barrels called Glissalube to provide better bridal grip to barrel wall.
Anyway, you should wind a mechanical watch periodically to keep the lubes active & moving.
The modern lubes are not suppose to dryout and last longer. Gone are the days of Porpoise jaw or Whale oils.
The are a plastic coatings used nowadays, Fix-A-Drop that allows the oils to stay in place & not wick or migrate.
Well, more information than you probably want or need to know.
Have a good watchmaker service the watch 4 - 7 years.
Mike