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The second of my two palate cleansers conjures up memories of previously well-trodden paths and consequently offers a potential source of comfort in providing something with which to ground myself.  As was common with many amateur watch fettlers of old, the first tentative steps into experiments in watch de-construction and reconstruction typically involved grappling with variations on the theme of the staple 1980’s Seiko 150m diver’s watch.  Tatty examples of the slim-cased Seiko 6309-729x series of diver’s watches were cheap and in plentiful supply in the late noughties and were the staple choice of the nascent watch-modding community at the time.  I produced my fair share of dubious transformations but also worked on a number of projects where the emphasis was more on restoration rather than transformation. 

A 3 by 3 gallery of photographs of Seiko 150m diver's watches

These included the classic cushion cased 6309-7040 as well as several examples of the quartz-powered 7548 variants, whose Japan domestic production dated from 1979 and whose case was to be used in the second generation 6309-7290 introduced about 3 years later.

Catalogue photo of two Seiko 7548 watches from 1979

The 7548-7000x series made its first appearance in the second volume of the 1979 JDM Catalogue.

I have documented the restoration of 7548’s on three occasions before (the three examples lining the bottom of the gallery shown above but described in more detail here, here and here), two of which the Pepsi model and one, the straight black bezel 7548-7000.  

It is an occupational hazard that in trawling for horological nuggets, inevitably you accumulate assorted examples of parts watches, some of which unexpectedly turn out to be worthy of revival in their own right.  One such example has resided in my waiting room for some time, its origins long since forgotten but which looks ripe for attention.  It is a Seiko 7548-700B from June 1981 and aside from the authentically-faded bezel, does not appear especially ravaged by the passage of time.

Front and back shots of a Seiko 7548-700B

The only fly in the ointment is that the movement is non-functioning, even with a fresh battery.  The movement looks otherwise tidy with no evidence of electrolyte leakage, nor damage to that vulnerable coil and the battery retaining spring, complete with its two screws, is present and correct.

Seiko 7548 movement in situ

If we take the movement out of the case, we see more clearly the lovely blue colour of the dial (this is one of reasons I like this model so much, preferring it to the more sober black on black of the 7548-7000) but also that the hands are corroded around their periphery. 

Seiko 7548 dial and hands with hands aligned to 8.45

I’ve aligned the hour and minute hand with the stationary seconds hand to aid removal.

Seiko 7548 dial with hands removed and resting on the dial

As I have documented 7548 rebuilds previously in some detail, I will fast-forward through the routine stuff, pausing to note anything of significance.  Having removed the dial and hands, the first order of business is to deconstruct the calendar side.

A 2 by 2 gallery of photos showing the dismantlng of the calendar side of the movement

Nothing much to note here other than that there is a degree of tarnish to the main plate that you might reasonably expect of a movement of this age and which has not previously been serviced.  I will note, however, the plastic day/date driving wheel because this will come to our attention again later during reassembly.

Similarly, the train side disassembly proceeded smoothly but once again we note in passing a significant degree of tarnish and more obviously dirt.

a 2 by 2 gallery of shots showing the dismantling of the train side of the movement

The non-running condition of the movement is perhaps accounted for in part by the encrusted state of some of the holes and bearings in the main plate, the centre wheel hole being a good example.

A close-up of the dirty centre wheel hole in the main plate

The technical manual recommends that the main plate is not cleaned in a watch cleaning machine but manually cleaned in benzine (petroleum spirit) and so this is what I did. 

A movement in a ramiken filled with petroleum fluid and with a toothbrush in shot

All of the other non-plastic and non-electrical components were pre-cleaned in the ultrasonic bath followed by the usual cycle through the watch cleaning machine.

Reassembly starts as usual with the setting parts before flipping over to assemble the gear train, fit the coil and then the circuit module.

A 2 by 2 gallery of the partial reassembly of the movement

It was only during the assembly of the calendar components that I hit upon the first snag and identified perhaps the main reason why this movement had not been functioning.  The plastic day/date driving wheel was binding on its post, and providing a degree of resistance to free rotation likely to have stopped the movement in its tracks. 

The calendar side of the movement showing the plastic day/date driving wheel

Apparently, the wheel had shrunk with age and, given that there is no way to reverse or correct this, it is no longer fit for purpose.  Happily, I have an embarrassment of spare 6309 and 7546 movements to call upon and quickly located a substitute which rotated on the post without any impediment.  With that hiccup resolved, the remaining calendar parts can be fitted.

The day and date disks fitted to the movement

Note the day disk jumper visible though the slot near the centre at the 7 o’clock position and the quickset day correction intermediate wheel through the slot adjacent to the word RING.  This intermediate wheel is called into action when the day corrector wheel mounted on the rocking lever swings across when the crown is rotated anti-clockwise whilst pulled out to the first clock position.

A close-up of the calendar side with an arrow indicating the postion of the day corrector intermediate wheel

At this point, the movement is complete but before we fit the dial and hands, we need to sort out those encrustations affecting the top edge surface of both hands.

A close-up of the two hands showing corrosion

My approach to this sort of problem in the past has been gentle cleaning with a tissue soaked in a little Cape Cod solution and wrapped around a pair of tweezers.  It is all too easy to take this a step too far and remove some of the plating, exposing the brass beneath so I proceed with caution to the point that the hands appear presentable, if not perfect.  Any excess filmy deposits from the Cape Cod is removed with petroleum spirit and then Rodico.  With that task complete, I refitted the dial and then all three hands.

The dial with all three hands refitted

The case is sharp and free from corrosion and all it needs is a clean, a new crystal and fresh gaskets.

A Seiko 7548 watch case with the crystal retaining ring removed

The case is dismantled and cleaned, aided by elbow grease, pegwood, toothbrush and toothpaste.  Mid-way through the reverse process, we pause at the point at which a new sapphire crystal has been introduced.

Cleaned case with a new crystal in position

This crystal has the correct profile, a frosted bevel and is free from distracting coatings.  It sits in an L-shaped gasket and is secured into position by a crystal retaining ring, pressed into place using a crystal press.

Fitting the crystal retaining ring using a Seiko crystal press

The last job before reuniting the movement with the case is to replace the worn-out gasket in the crown.

A close-up of the worn crown gasket removed from the crown, also in shot

With a fresh gasket greased and fitted, the spring, washer and female part of the two-part stem can be reassembled.

The reassembled crown with fresh gasket fitted

We are all set now to reunite the movement and case.

Movement refitted to the case, viewed from the rear

At this point we can confirm that everything works in situ by fitting a new battery.

A fresh battery fitted to the movement

It does.  Case back fitted and we can check the alignment of the seconds hand with the markers as it works its way around the dial.

Movement refitted to the case, viewed from the front.  The bezel is not yet fitted

All that remains is to grease and fit a new gasket to the bezel and press it into place prior to selecting a strap.  My choice for the latter employs the buckle half of the original GL831 paired with an aged but undersized partner that does the job for the moment, but which will need replacing in due course.

A slanted view of the finished watch, fitted to a strap

The stiff and weathered old strap complements the faded appearance of the watch itself although the pick n’ mix lower half can’t quite bridge the 22 mm distance between the two lower lugs!

A face-on view of the finished watch on its strap

Clearly, after all these years I am still drawn to these watches in spite of the fact that they violate my private code of practice never to wear or own watches with 22 mm lugs.  In one sense, I comply with that principle because I rarely wear any 22mm lugged watches that pass through my ownership (my Seiko 6306 looks up at me dolefully from time to time as I ignore it for other slimmer-hipped competition) but I still like them.  There is something ‘just right’ about this era of Seiko diver’s watch.  It is uniquely styled, tough, very well engineered and fit for purpose.  It’s just that it’s not my sort of watch.  Even though it is.