On My Bench - Seiko 7549-7010 Deconstructed

Here we have a Seiko 7549-7010, AKA the "Tuna Can" in component form.

Edit: It has been bought to my attention that this is NOT a Baby Tuna!

Hi Jim,

Saw your On My Bench post for the 7549 ( 47mm diam) and noted you referred to this watch as the "baby tuna"

Whilst it's a baby compared to the original grandfather tuna (50.5mm diam) I've always associated the "baby tuna" with the 5M23A series which had a plastic shroud and 43mm in diameter.

The 7549 was the first professional 300m quartz diver ever produced and because it had the silver metal shroud was nicknamed "Tuna Can"

Interested to see if any other WIS pick up on this.

So the introduction has been updated accordingly.



Not much different to the one I just completed except for the case design, which I'll get to later.

I have to say, your "On My Bench" series are some of my favorite threads on this forum to read through. Thank you so much for the time you put into writing these up and the pics you create for them. As someone that loves taking things apart, I enjoy living vicariously through these posts 👍

I'll see if I can keep you entertained then 😉.

First step was to remove the bezel shroud. Held in by three screws, it requires the screwdriver with the correct tip. Us a standard Phillips head and you risk deforming the slots in the screw head. I use JIS (Japanese Industrial Standard) screwdrivers on any screw coming from Japan, from motorcycles all the way down to watches.



Note that I'm doing this part in my garage on a clean hand towel.

With the bezel shroud off, we can see the gunk and corrosion that has built up over time.



With the shroud off, I can clean the case to prevent "detritus" getting into the case when I open it. I think it needs it!

So here we go, cleaning time.



Most of the cleaning will be done around the caseback using a soft brush and a softwood stick.



With the case now clean enough to open it can go back into the watch room. Sure can't stay here!

Caseback comes off.

And then it all happens as described in the other threads.

With all of the movement parts safe and sound I can turn my attention the the case.

After removing the bezel, I found even more crud.



So it was back to the garage to clean it up so I don't get gunk all over my casebook tool.

A quick change of pins on the caseback tool..........



and the remainder of the case was disassembled.



The nylon glass fixing gasket (red arrow) was so old it disintegrated, so I'm waiting on a replacement from the US.

The bezel was soaked overnight in mild soap solution and then I started cleaning the bezel notches using my "bezel holding jig".



One notch at a time.



Next I'll clean the case, but first I'd better change the wash fluid 😲.
Note all the crud that gets removed and won't pollute my ultrasonic solutions when I clean the parts (except the bezel).

There’s a proper English word for this stage: eeeeeew!

Time to gather up all of the bits and get them ready to clean.
Into the basket they go.



and off for a nice bath in my vintage cleaning machine.




While that was happening, the case was cleaned by hand again, then given an ultrasonic bath.

Came up quite well I think. Just a few tiny corrosion pits left, but I don't think it's worth me buying a laser welder.

Things on hold ATM, waiting for parts, so I'll just post random pics.

I noticed the stem extension wouldn't sit correctly.
It appears that a substitute spring was fitted and the top coil hadn't been flattened, just cut, so the stem washer was seated at an angle.

I put the spring on a 1.0mm dial pivot wire in a lathe collet and used a Dremel wheel to face the spring.

This resulted in an improvement in alignment but also in a loose joint.



Rather than try to source a replacement spring, I went to the spares and got another stem washer to remove the slack in the connection.

How long does it take?

I guess there's a reason for huge packages waiting for a cargo slot, but my tiny package?




I don't like to have more than one watch at a time on the bench (not as organised as @Archer, @ChrisN et al 😉) so we just patiently wait for the postman to cometh.

I think the logistics is the bit that brings a lot of independent watchmakers a bit unstuck when they’re working on their own, its the un-fun part that starts to really eat your time when you begin servicing a lot of pieces.

Almost here .

Only took FIVE DAYS to get from Sydney to Melbourne 🙄.



Oh well, enough complaining, time to get back to work on this one and hope there's no more overseas parts need next time.

And just when you think you can crack on with it, family issues interrupt.
But my impatience is nothing compared to CAT scans, MRIs, lumbar punctures, brain surgery and the rest of the things that go with all that.
🙁

Anyway, I managed to get back to it today so I got the case ready for the new crystal.



The edge of the new crystal has to be carefully lubricated so that only the tiniest hint of silicone is present on the lower edge. In fact, the edge is wiped with a chamois pad after lubing so there's no chance of excess lube going anywhere. The crystal is now pressed in by hand and checked for correct seating in the gasket.



Next step is to fit the nylon gasket into the step on the side of the crystal. It's used as a bearing surface so that the steel crystal ring doesn't graunch the crystal as it gets tightened. That done, the screw down ring is fitted and finger tightened, and then it's over to the other bench to tension it down.



Lastly, the crown is fitted and the caseback seal is lubed and fitted and the casebook installed and tensioned.



Then a water tightness test is performed.



No bubbles were evident under the heaviest vacuum I could manage with my "tester" and a condensation check showed no water on the crystal.

I really need to get myself a proper waterproof tester though.
Raiding the kitchen cupboards for "tools" gets me some funny looks from Ms JiO 😁.