Mandaue, Author at RK Watch Service

Citizen’s first digital TC movement, the caliber 1930

original title: Exceed ENH-205 with caliber 1930
Vintage find with Citizen’s first thermocompensated movement, the cal. 1930. (But not necessarily the inaugural watch model of 1981.)

There is also a darker dial ENH-200. Catalog page shared by @Citizen _collector
[ATTACH type=”full”…

Citizen’s first digital TC movement, the caliber 1930

High Accuracy Quartz watches

Wearing AW on ankle

NYTimes: “
A small but growing movement of ankle-watch acolytes has been afoot for a couple of years, as various users of …

Apple Watches

70s and 80s Citizen quartz service manuals

I have obtained a set of 40+ year old of service manuals, guided to the listing by @CitizenPromaster. Thank you, sir.

The service manuals consist of 4 binders. Pages are cardstock, clearly made to last. There are also overleaf pages for complex diagra…

Citizen

2024 Seiko patent applications for electronically regulating mechanical watches (both SD and non-SD types)

EDIT: there are two Seiko applications, taking different approaches. See post #7 for the SD-type one.

Below is the non-SD type:
Here is a new US patent application (October 2024 publication) I found while looking for Spring Drive patents:

…

Grand Seiko

2024 Seiko patent application for an electronically-regulated mechanical watch (not SD)

Here is a new US patent application (October 2024 publication) I found while looking for Spring Drive patents:

It is NOT Spring Drive as we understand it, because there is still an escape wheel (#21 in the illustration) and a pallet fork (#22). There is however something more than a balance wheel (everything to the right of #22).

And it is NOT necessarily a quartz regulator. There is only a ‘speed governing mechanism…

2024 Seiko patent application for an electronically-regulated mechanical watch (not SD)

Grand Seiko

Akio Naito interviews

The better one is with Time & Tide: Akio Naito, President Seiko Watch Corporation | INTERVIEW

—

Another…

Akio Naito interviews

Grand Seiko

Seiko 2-way inductive communication with HAQ calibers

Miyahara (2003) Development of a non-contact annual deviation accuracy and guarantee system appears to describe Seiko’s factory regulation, adjustment and diagnostic system for HAQ mass-production.

The system described:

Was motivated to make HAQ production more efficient by avoiding stray capacitance effects.
Is a…

Seiko 2-way inductive communication with HAQ calibers

High Accuracy Quartz watches

Seiko technical paper on the 9RA-series Spring Drive

Solely due to the generosity of @CitizenPromaster , I have come across a gold mine of technical information on Seiko’s 9RA second-generation Spring Drive movement in the form of a 14-page Japanese-language technical paper published by the Japan Horological Society (日本時計学会) in their journal メカトロニクス (translates to ‘Micromechatronics’)

Out of respect for possible copyright, I will not (yet) post the entire paper…

Seiko technical paper on the 9RA-series Spring Drive

The 1995 Japanese Industrial Standard for HAQ and its fatal flaw

JIS B 7025 in its 1995 edition is the current Japanese standard for ‘accuracy indication’, i.e. how makers may advertise the accuracy of quartz watches (and clocks).

First the good news
At the tier of ‘annual accuracy’, the JIS mandates that manufacturers measure three things:

1) Temperature variation Vt
2) Aging variation Va
3) Battery voltage drop variation Ve

These are added together and…

The 1995 Japanese Industrial Standard for HAQ and its fatal flaw

High Accuracy Quartz watches

Horological Institute of Japan and its journal

I have mentioned the HIJ a few times before, but my very first was in the cal. 2722 thread when I stumbled onto primary sources for the significance of te Citizen cal. 1930.

"The Horological Institute of Japan is the only academic organization sp…

High Accuracy Quartz watches

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