9/13/2023 0 Comments Seiko 620![]() Gently press down while pulling the stem out. There is a lever with a small indentation for your tool. To remove the stem, make sure the crown is in position 0 or normal position (not date or time setting position). Crown Position Functions:Ġ (against the case): Clockwise = Manual Winding / Counterclockwise = Nothingġ (pulled out one click): Clockwise = Day of the week setting / Counterclockwise = Date settingĢ (pulled out two clicks): Time setting clockwise and counterclockwise Stem Removal: To fully wind the mainspring, turn the crown a minimum of 55 times. The caliber 6R20 holds a power reserve of at least 45 hours. In such a case, consult the retailer from whom the watch was purchased since the watch requires repair, including demagnetizing. The parts of the watch may become magnetized depending on the extent of the effect. When affected by external strong magnetism, a mechanical watch may loss/gain time temporarily.Relatively steady accuracy can be obtained by wearing the watch on the wrist frequently for the self-winding type and winding up the mainspring fully everyday at a fixed time to move it regularly for the wind-up mechanical type.As the mainspring unwinds, the force weakens. The driving force of the mainspring that powers mechanical watches varies between when it is fully wound and immediately before it is unwound. In order to improve accuracy, it is important to regularly supply energy to the balance that controls the speed of the gears.Mechanical watches tend to lose time at high temperatures while they tend to gain time at low temperatures. This exerts an effect on the accuracy of the watches. The key components in mechanical watches are made of metals which expand or contract depending on temperatures due to metal properties.The accuracy of mechanical watches may not fall within the specified range of time accuracy because of loss/gain changes due to the conditions of use, such as the length of time during which the watch is worn on the wrist, arm movement, whether the mainspring is wound up fully or not, etc.6R20 has an average accuracy rating of -15/+25 seconds per day in normal temperature conditions (between 5 – 35 degrees C). Also note: the span locations may vary depending on model. In Seiko’s own words, they describe the placement on the 6R20 as being “center aspect” and the 6R21 as “9 o’clock aspect”. On the 6R21, the PR indicator spans from around 7:00 (full) to 11:00 (empty), with the pointer hand positioned closer to the center of the dial. On the 6R20, the PR indicator spans from 8:00 (empty) to 11:00 (full), with the indicator hand being closer to the edge of the dial. ![]() There is a similar caliber 6R21 with the main difference being the power reserve indicator display style. A few of the differences are outlined in the chart below:Ĭentral hours, central minutes, central seconds, date at 3:00Ĭentral hours, central minutes, central sweeping seconds, power reserve indicator between 8:00 and 11:00, day of the week subdial at 3:00, date subdial at 6:00 6R20 VS 6R15:Īlthough based on the 6R15 framework, the 6R20 reads much differently on paper – and on the wrist. Interesting note: The calibre 6R20 shares the same instruction manual as the 6R21, 6R24 and 6R27 movements. The caliber 6R15 is the base caliber for 6R series movements such as the 6R20 discussed here (as well as the 6R21, and 6R24, and 6R27). ![]() Early models of the 6R20 At the time of this post, the latest and current version of this movement is the 6R20A (if this changes, please update the comments below). The subsequent letter variations indicate evolution stages in the movements development. The general caliber number is 6R20, with 6R20A being the first version. Some of the topics covered in this caliber listing:
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