In flagrant violation of my self-imposed rule not to buy watches with lug widths larger than 20mm, I find myself in possession of a Seiko 7548-7000 dating from June 1982 (22mm in case you were wondering). My excuse is that the bid I submitted was not entirely serious but ended up winning the auction, probably because other potentially interested parties were put off by the watch having been described as unresponsive to the fitment of a fresh battery. I confess too to a certain fondness for the model, largely because my first semi-serious attempt at a watch refurb was the fettling of a pepsi variant of the same (see here). It is also a watch to be respected because its design was born from the tail end of a golden period of creativity for Seiko and, as a result, it is a watch whose quality shines through, unencumbered by the air of penny pinching evident in the second generation 6309 automatic diver’s watch introduced three or four years later and with whom it shared its case design.
The auction photos suggested that this particular watch was in tip top nick, non-functioning movement notwithstanding, and with it in hand, that impression is not undermined.
For sure, it is a little dirty but it looks to have been very well cared for over its 33 year life time, with the dial and hands in particular looking super, the bezel original and only sporting a few minor scratches and the crown and case tube still in possession of the full quota of thread. With a movement as potentially accurate as this robust old quartz, it is perhaps not surprising that previous owners might not have had cause to undo the crown very often.
It doesn’t look either that this watch had seen much watchmaker action: the case back shows two dimples on its timeline indicating battery changes in 1985 and 1991
although, any since 1994 would not have appeared on the case back, I suppose. Still, the movement looks clean with only some tarnishing to the model number plate on the green circuit block betraying the watch’s age.
The battery is missing from this shot but when I received it, one was fitted and the watch not running, as advertised; a substitute yielded nothing in the way of meaningful action either. Its non-functioning state was enough to prompt me to pick up a very cheap but working 7546 quartz watch from eBay to farm for parts as required (I was thinking at the time that the coil was probably shot).
Slipping the movement out of the case and the dial looks every bit as good as hinted at from the exterior view, barring a slight mark to the left of the 5 marker.
Dial off and we see a calendar-side layout all but identical to the 6309 on which this movement is based
with pretty much everything looking essentially mint. The resistance offered up by the hands when I removed them suggested that this is the first time anyone has gained access to the movement innards since 1982. I’ll skip the breakdown of this side of the movement as we’ve been here before with the 6309 (see here, for example) and concentrate instead on the relative unfamiliarity of the train and circuit side.
The layout is pretty conventional with the train wheels and bridge sat in the centre, the coil at the bottom and the quartz oscillator and circuit hidden on the reverse side to the left. The gold coloured screw to the right of the movement nameplate is a trimmer condenser, used to regulate the timing of the movement.
The green circuit block is secured by four screws, two of which also secure the battery-holding spring. With it removed and turned over we can see the quartz oscillator and reset pin, the latter coming into play when the crown is pulled out to the time-setting position.
The removal of the circuit block allows access to the coil and train wheel bridge.
A slight hiccough follows because, having removed the crown with it in the time-setting position, the second setting lever (effectively the equivalent of a hacking lever) is sitting snugly against the fourth wheel, making extraction of any of the train wheels ill-advised.
Refitting the crown and stem and resetting to the normal position frees up the fourth wheel
permitting the removal of the train wheels and providing access to the centre wheel bridge.
The tarnishing of the model number plate on the circuit block was something I wanted to sort during the cleaning process. Obviously, attempting to clean it in situ is inadvisable but it is easy enough to remove by pushing the securing tabs from the rear.
Following cleaning of all of the non-electrical movement parts in the watch cleaning machine, reassembly proceeds as follows: First up, fit and lubricate, as required, the clutch and stem followed by the setting lever, yoke and setting lever spring.
Turn the movement over and fit the centre wheel and positive battery terminal connector
followed by the centre wheel bridge, rotor stator and reset lever.
The train wheels, step rotor, second setting lever and reset lever come next, with the crown set to its normal position to aid fitment of the second setting lever.
Setting the crown to its second position frees the lower part of the reset lever to move downwards against the sprung load exerted by its upper part, with the end of the stem no long sitting against the pin to the rear of the reset lever. This downwards movement simultaneously allows the second setting lever to rotate clockwise and make contact with the teeth of the fourth wheel and the end of the reset lever to move downwards and make contact with the reset pin on the rear of the circuit block.
The contact of the reset lever with the reset pin stops the output signal from the circuit block but maintains current to the quartz oscillator so that it is ready to start again when the crown is pushed back to the normal position.
The remaining steps in the reassembly of the movement are straightforward but in taking them, we need to test the function of the original coil and circuit. So, first refit the original coil and anti-magnetic shield followed by the circuit block, now reunited with the cleaned model number plate.
I secured the circuit block with a pair of screws borrowed from that spare 7546 movement because I did not want to refit the battery securing spring just yet. Pressing a fresh battery into the battery holder and I was relieved to see the movement spring into life. It looks as though it was just dirt and dried out lubrication that was preventing it from operating rather than any faults with any of the electrical components and so for the moment, that 7546 can breath easy.
Moving back to the calendar side, reassembly appeared to have gone smoothly but when testing the operation of the setting and quickset, I noticed that during the time setting operation, the rotation of the setting wheel was dragging the day/date correcting gear across to the intermediate day correction wheel, mounted on the minute wheel bridge, causing the latter to rotate. With the day wheel fitted this would result in the day wheel rotating inappropriately during the time-setting operation.
The reason it was doing this was that the setting wheel lever was not sitting low enough against the movement with the result that the underside framework was not staying hooked over the pin on the main plate (illustrated below in a photo of a spare 6309), thereby allowing the whole shebang to drag to the left.
I removed both the setting wheel lever and minute wheel bridge and gently bent both downwards slightly, with the result that the latter exerted a stronger force on the former when tightened down and the setting wheel lever then sat slightly lower. A retest and all seems well.
Attention now turns to the case. The usual breakdown into constituent parts
is followed by a thorough clean. Out with the old gaskets and crystal
and in with the new, together with a fresh battery.
The crystal, incidentally, is a tempered mineral facsimile of the original, complete with frosted chamfer and sourced from eBay seller kleinvintagewatchparts. You can see that lovely frosted chamfer in this shot of the crystal refitted to the case and awaiting the crystal retaining ring.
With the dial and hands refitted to the movement and the battery retaining spring back in position, it is time to fit the movement to the case,
close up the case back and turn over
The watch would originally have been fitted with a GL831 straight-vented rubber strap rather than the Z22 curved-vent strap it came on
and so with a modern equivalent secured (4FZ0AZ), we are all set to wrap this one up.
All that remains is to check the timekeeping and regulate as required. In this case, the watch was running a little fast for the first day or so but an eighth turn clockwise to the trimmer condenser and the watch has lost just under a second in the past 5 days, well within the specified accuracy of 15 seconds gain or loss per month. Let’s conclude with a wrist shot on the new strap.
David Bidwell said:
What a classic looking, well built quartz diver. Beautiful job bringing it back to life. By the way did you leak test it too?
Hi David, thanks very much. I’ve not yet got around to leak testing but with fresh gaskets and no pitting to any surfaces, I’ve no reason to doubt its water resistance.
I have the same watch. I bought it in Japan in 1982 while stationed in USS Grayback SS574. Can you tell me the battery size? I can’t read it! Thanks!
Always nice to hear stories of folk buying these at the time they were originally available new – thanks. The battery is a 301 Silver Oxide.
I have been reading through your posts about the 7548. I must thank you for your detail throughout these posts! I have a 7548 diver that I purchased from Japan and you can see the second hand twitch, but it does not run. I took the battery back out of it and I will prepare for servicing. I have experience with the 6309 cal. as far as servicing so hopefully all will be well.
If the circuit is uncontaminated by battery electrolyte and the coil is intact, then it probably just needs a clean and lubrication. The dial side is identical to the 6309 and so if you’ve worked on the latter then it should be familiar territory. Good luck!
Great walkthrough – used it as a guide when servicing my 7548 :).
Love these built-like-a-tank-and-to-last watches.
Dan O'Connor said:
Hi Martin, I enjoy reading through your posts and hope to get to watch disassembly at some point. In one of your earlier posts, and maybe here, you reference the 7548 as a mid grade diver in the Seiko lineup. Outside of the shrouded versions 7549, what else in the early eighties would have been a higher level diver offered by Seiko? I had read that the 7548 stayed in Japan during this period and the auto diver design and assembly team was moved to other countries, which kind of hints that these were the flagships of the lineup. What else did they offer in a higher finish or movement? Thanks, Dan
Hi Dan, my view on the hierarchy is defined by the relationship that was established between the 62MAS and 6105 150m divers of the early to late 1960’s and the higher end 300m 6215-7000 that appeared in 1967, followed by the high-beat 6159-7001 a year later. This higher end position was subsequently occupied by the 600m 6159-7010 and 7549 Tuna’s of the mid to late 1970’s (the latter in the context of the emergence of quartz technology as the state of the art) and later the 7C46 1000m Tuna of the mid 1980’s and beyond.
As soon as that first 6215 300m professional divers watch appeared in 1967, the 150m (and latterly 200m watches) could no longer be regarded as anything other than mid-tier watches, albeit watches that could be rightly regarded as professional divers watches. The fitment of quartz movements to the high end divers from the late 1970’s should not detract from the fact that these watches were constructed to a much higher level than the 150m 6309 and 7548 divers watches of the same period.
Dan O'Connor said:
Thank you! The fitment of quartz does not detract at all as this was the leading technology at the time. I’ve taken a shine to the quartz diver’s of this era for their grab and go robustness. My first real watch was a gold faced Seiko 200m diver 5H26 quartz as a graduation gift. In my recent research of this model I’ve stumbled into this great resource, and have since purchased a 7548 and a 7549 to join the 5H26. It looks like I have the 3 tiers of build quality covered now and enjoying them all. I honestly went through the phase where I frowned on the quartz and had to have an auto, but practicality has put them idle in the drawer most of the time.
You are more fortunate than I. Thus far, I’ve yet to own a high end Seiko diver and those that I hanker after (6215 and 6159-7000’s) are now comfortably out of reach! Perhaps a modern MM300 is the answer 🙂
Dan O'Connor said:
Hi Martin, I’m ordering some parts for this same model. I got the crystal from spencer Klien, I found the 3 gaskets. Does one need to change the crystal gasket normally? I have not been able to find that as easily. Second question, this watch has a click ball. My watch has the ball, but the bezel only clicks during half the rotation unless I push down harder. I have confirmed that this is the case with other bezels on same watch, and those bezels click fine on another 6309. My guess is the crystal ring is not seated properly. Does that sound correct with those symptoms? I guess my next purchase is a crystal press. Thanks.
The crystal gaskets are usually in decent condition in my experience and so more often than not just need a clean. Make sure not to use any lubrication on the crystal gasket.
Your click problem sounds odd and suggests that the bezel is not sitting flat against the case. I can’t really offer any solutions though. Good luck!
Fantastic piece. Models like this really change my opinion of quartz movements.
Andrew Godber said:
I’m the proud owner of a 1982 7548-7000 which has been looked after by Neville Cox for Battery changes, replacement hands and bezel as needed. I have worn it continuously every day since I bought it. Not keeping it as a collectors piece, just my everyday wear. Does anybody have an ideas about where I can get a replacement face from?
It is always wonderful to hear from people who’ve owned and used such watches from new and for whom the patina is all self-inflicted!
As to a replacement dial, finding an original will be very difficult – close to impossible – unless sourced from a donor watch which has other issues. There are aftermarket options, but anything with Seiko branding that is produced by a third party will be of poor quality and to boot, in my book, constitutes fakery and so personally, I would rule out that option. You’ve not said why you wish to replace the dial. If it is just a matter of the lume, then you could consider getting it relumed but you will need to do some research to find someone who really knows what they are doing.
Alan Bolitho said:
I am about to advertise a 1982 7548-7000 for parts and the face is in excellent condition.It also has a Seiko metal band.
An ameteur watchmaker tried to get it going but it is either dirty (like Martin’s) or the coil is broken.
I give Martin permission to share my contact details with you as I would rather it go to a good home than an unknown person. email@example.com
Fantastic read and a great job :). I have a very tired old 7548, I’d like to restore it, but the hands need cleaning, can i ask how you cleaned yours?
I don’t think these needed much more than a careful wipe with soft tissue wetted with lighter fluid and/or watchmaker’s putty. If you want to see a more extreme hands makeover, check out the most recent entries on the 6309-7040.
Thanks! Will do
Adrian Orozco said:
Hello Martin, I have the same watch, the serial number is 002964, imagine how old it is. I need a new green circuit block and a new calendar slide with the date in english and japanese, just like the one you show here. How can I get those parts? I live in Mexico City.
Hi Adrian, probably the easiest solution to the circuit block problem is to find a used 7546 watch on eBay. The circuit block is identical to that of the 7548 but just marked differently. Ideally, you might even find a crown at 4 7546 with English/Kanji day disk and kill two birds with one stone. You could also try one of the specialist Seiko watch fora sales corners or post a WTB. Good luck!
Adrian Orozco said:
Hi Martin, please help me repair my Seiko Watch 7548-7000. About one and a half year ago, I was on vacations at the beach, and without notice it, the crown was not correctly closed and some water got inside my watch. I did not take it to a repair workshop immediatley, so the circuit block and the english/kanji day disk broke down.
Please tell me where in the US I can send my watch so it can be repair, or if you can do it I will be very happy.
Thank you very much,
Hi Adrian, you might give Spencer Klein a try. I believe he is located in Colorado.
Adrian Orozco said:
Thank you very much Martin, of couse I will try to contact him.
JOHN CLIFFORD said:
This is a great article, well-written as is the rest of your blog posts. I have the Pepsi version / 7548-700L, bought new in 1985, and I plan to use your posts on these watches to help me replace the battery and bezel insert. Would you be willing to provide a brief list of the tools that you find necessary for this type of work, or perhaps even write a blogpost on the books you’ve read and the steps you’ve taken to get into proficient amateur watch repair and restoration? Thanks!
Hi John, for the bezel insert, I would recommend you buy a Seiko style casing knife (yellow handle on Cousins’ site) and for the battery change, you will need a case opener, a suitable flat bladed jeweler’s screwdriver (to remove one end of the battery retaining strap) and maybe a plastic component probe for holding down the retaining spring as you loosen the screw. I’d also recommend a pair of tweezers. If the case back and/or bezel gaskets need replacing you’ll need to do so but either way you’ll need some silicone gasket grease. For the case back opener and tweezers, you could give Rolson a try. Good value and decent. In particular I really like their two prong adjustable hand held case back opener. Good luck!
John Hershey said:
I picked up a 7548-7000 on the cheap (and in pieces) a few days ago. I’ve sorted everything out and got it working with one problem – the stem release lever is stuck in the down position and so the stem doesn’t engage the yoke mechanism and just slides in and out. Any suggestions to get it to release? I have the tools and experience (at least enough to get me into trouble!) to remove the hands/dial but I’m hoping I can avoid that as the dial is quite nice.
Also, the inner day wheel is advancing normally but the the outer date wheel is not advancing. I’m hoping that if I get the stem release working maybe it will start moving, or is this just wishful thinking?
Any advice you can provide is greatly appreciated.
I’m afraid there are no reliable short cuts to sorting it properly! Given that you also have a problem with the calendar, there is no excuse not to go in from the top. The only way you are going to be able to resolve both issues is to remove the dial and hands, investigate, dismantle as required and reassemble. Sorry not to be able to divulge some sorcerer’s secret to doing it the easy way 🙂 Good luck!
John Hershey said:
Thanks for the advice
John Hershey said:
Any chance you’d be willing to take a crack at mine (to be paid of course)?
Sorry John, but this really is just a hobby for me. I barely have enough time as it is to attend to my own pile of basket cases. If you are in the UK, you might give Richard Askham a try. A thoroughly decent bloke and an excellent watchmaker.
KW Wai said:
Nice and detailed, it can be used as a useful guide to refurbish a 7548.
Do you know whether SKX 007/009 hands are able to fit the 7548?
Yes, the SKX hands will fit 7548.
KW Wai said:
Thank you Martin for the information. I will start gathering some replacement parts for my little 7548 revival (cosmetically).
Hi! What did you use to clean the case?
I usually start with pegwood to sort out any stubborn solid deposits, followed by ultrasonic bath and/or toothbrush with toothpaste. All followed by a rinse in clean water and a through dry.
Do you now what kind of lume Seiko used with 7548? I can see a T on the dial and mayby that stands for tritium and I have also read that they used promethium in this?
I’m afraid not – sorry. I am not sure though that the T on dial dial has anything to do with lume type.
Any lead on spare parts – I have a seiko 7548-700B – bought it in the Falkland Islands just after the cease fire in 1982 – the lume has gone and I would like to bring it back to life. Still working well otherwise.
A relume is the only option if you want to keep the dial correct for the watch. You won’t find a replacement dial with working lume now. Or even one with dead lume!
Bummer..thanks for getting back to me. Any leads for a re-lume? Ain’t no way I can tackle that.
Not really. All but one of my professional relumer experiences have been very disappointing and the one that wasn’t has disappeared.
First of all thank you for a very good blog and also for the videos. It is indeed a joy to watch and right down the trend of ASMR.
When water or moist enters these quartz watches, what is the typical course of malfunction?
The reason for asking is that I have a 7C43-7000 in non operating state due to moist inside the case. I have not yet disasebled the watch, but I am suspecting the circuit and coil.
It turs out that a cheap doner is not easy to find. Do you know if these parts are interchangeable between 7546,7548 and 7C43?
Thanks in advance.
Hi Sten, thank you for your nice comments about the blog – that is appreciated. The most obvious effect of water ingress on a quartz watch is that is may damage the circuit but it could also result in some impediment to the mechanical components. It is really difficult to know what until you gain access and test and dismantle the movement. I am pretty sure that there is essentially no parts interchangeability between 7C43 and 7548 – they are two completely different calibres. It may be possible to drop a 7548 into a 7C43 case but I’ve not found any definitive opinion on that which suggests that maybe it’s not possible. The 7C43 coil assembly is available on Cousins site but not the circuit. That’s as much as I can offer I’m afraid. Good luck!
Hi Martin, I hope it is ok to ask you yet another question. The tecsheet specifies 3 different lubricants. Mobius A (which I believe can be replaced by 9010), Seiko S-6 and Moebius F. Seiko S-6 I think can be be replaced by HP1300? I haven’t found anything on the Moebius F. Do you know the replacement for these 3 lubricants?
Thanks in advance.
Hi Sten, you shouldn’t necessarily take my choices as gospel but here they are: 9010 for Moebius A; 9104 (HP1300) for S6; Either 9104 or a thicker grease such as 9501 for Moebius V and then 8201 for S2. The question of barrel lubrication is vexed and a matter for experimentation. All the best Martin
Hi Martin. I’m working on a 6458-6000 at the moment – kind of a smaller version of the 7548 externally but the movement looks quite different. Somehow snapped the stem. Do you know if it is a shared part with any other movements?
I also pulled the old, scratched crystal and installed a few different ones to try. Cousins’s flat crystals didn’t have enough bevel on them and so the crystal retaining ring wouldn’t go on at all. The original crystal is 2.5mm thick with about 1mm vertical wall before 1.5mm of bevel whereas Cousins’s was the opposite. Could you advise where I could get a suitable 28.0×2.5mm bevelled flat crystal if I wanted to keep the original look?
The Sternkreuz MD low double-dome crystal did work quite well, and looks similar to my 7C43-6010’s domed crystal so I’ll try that for now. One problem though: the crystal retaining ring seems impossible to push on all the way, leaving a very slight gap under it and making the bezel very tight to turn, even though the retaining ring and bezel both snap into place quite positively. I thought this might be due to the shape of the crystal so tried the original crystal back in but the same thing happened. I’m using a cheap crystal press but might try to push it on more using my dies in a vice. What do you think? The retaining ring was on there incedibly tight when I received the watch and it took a long time with a penknife to work it off. Someone on a Facebook group suggested that I might have stretched out the crystal gasket and should replace it. Does that sound likely to you, and where might I get a replacement gasket to try?
Hi, I believe that the part number for your stem is 372640 but I don’t know whether this is unique to the 6458 or not. Other related 64 series movements seem to use the part 354640.
As to the crystal, I am not going to be of any help I’m afraid. The dimensions of these crytals really is important if you want both to be able to fit the crystal retaining ring AND clear the rotating ring and for that reason, OEM or crystals otherwise designed specifically for your watch are probably the only way to go. I would note that this is the reason why I have never bought a 64 series diver!
Mike Caplan said:
Hi David. I inherited a 7548-700F from my father. I only dug it out it today. I notice your days are in English and Japanese? Mine in English and French, is this common?
Also, do you know when this model was made?
The language combination will be market dependent so yours European market probably, mine Japanese domestic. As to age, you will be able to date it accurately from the serial number: the first digit is the year; the second the month. The most likely decade the 80s bit if it’s an early watch then maybe late 70s.
Chris W. said:
As a young US Navy sailor I purchased a Seiko 150M 7548-7000 from the Navy Exchange at Naval Station Yokosuka Japan in 1984. This model has English/Spanish day text so I assume it was targeted to US markets and that’s why it was at the US Navy base in Yokosuka Japan.
I have taken great care and the watch is in excellent condition less the faded luminosity of the hands/face and obvious replacement of battery, watch band, and one crystal replacement.
I have come to covet this watch as it was the first “real” watch I had purchased on my own, and it will be passed down to my heirs upon my demise. So my question is: Do you have a recommended preventative maintenance plan that will help me to continue maintain its excellent condition? It is my daily work watch, and will continue to be so, but with an eye towards maintaining that same excellent condition 20+ years from now.
I just found your website today and am very much enjoying looking through your articles. Thanks for all the posts you have made on this watch.
Hi Chris, many thanks for taking the time to comment and pose your question. I am glad to hear that you found the content helpful. To address your question, I would highlight two key things to pay attention to, one of which particularly important for any watch likely to be exposed to water: 1) Replace the gaskets periodically. The easiest to do is the caseback gasket but the crown gasket is also relatively straightforward and a common item to harden and crack. The crystal gaskets tend to age very well and in my experience just need a good clean when replacing the crystal at service. 2) For any quartz watch, never leave a spent battery in the watch if you set it to one side for a while. They commonly leak electrolyte once they have reached the end of their life and that can kill the electronic module. The 7548 is a very robust movement otherwise but will benefit from a service from time to time. That’s about it I think.
VEI HONG said:
Hi. Appreciated the post.
I have a 1982 Jan Seiko 7548 too that I I bought it after seeing your post. For I was born in 82 too and I have an skx to pair with it.
Soon as I got it, I took it apart to get the case lightly polished and clean the few metal parts especially those gunk that hide in the bezel and crystal retainer.
Absolutely love it and now sourcing part to change the crystal and probably the crystal gasket too.
Just wondering do you know what’s the difference between 320W34GA00
Well done on the clean up and good to hear you are enjoying your 7548. To answer your question, the 320W34GA00 is the correct crystal for the 7548 as well as 6309 150m divers watches. It is a flat crystal with a frosted bevel. The 320W10GN is the correct crystal for the earlier 6105 divers watches. It comes in a number of different variations but is most commonly double domed, with a marked inner dome, a much more gentle outer dome and with a pronouced clear bevel. The bottom edge of the crystal is frosted. The 320W10GN will fit the later 6309/7548 and this is a common mod but in my view, the later watches are better with the correct, flat crystal. But that is, of course, just an opinion!
Jr sanchez said:
Hi,can you please repair my late dad watch? Its the same watch that you repair. Please it has sentimental value to me.thanks
I’m sorry but I don’t take in work at all. I only work on my own watches. I hope you find someone to help you. All the best Martin