On My Bench - Seiko 7548-700B

While waiting for parts for another watch, I decided to get to work on another one that had turned up.

The owner wanted new seals and battery and asked me to see if I could fix a problem with the setting mechanism.

It's a nice Seiko quartz diver, you can see the state of the crystal, and the dial underneath is in excellent condition, although it's hard to tell in this shot.



Caseback is in good condition, doesn't look like anybody has used scissors or circlip piers to open it.



First thing is to open it.



Movement looks OK, no signs of water entry or battery leakage.

Disassembly.

Movement is taken out and the hands removed to be stored for safekeeping along with the movement (in seperate containers).



Then we can pop the bezel off. Eeew....cruddy.



Glass ring and glass/gasket and dial ring all removed and ready for cleaning.
(Pictures are not just for your enjoyment, they're a reference so I put everything back in the right order, not an issue here, but some assemblies are a bit more complex).

After some brushing and ultrasonic cleaning (not the dial ring though!), the case parts are ready to be put back together.



The dial ring is fitted, then the gasket ring and gasket, then the glass is pressed in.



The glass bezel is pressed on and then we're ready for the rotating bezel to go on after the gasket is lubricated and fitted.

The crown stem assembly is next, it was pretty dirty and I only took a pic of the grease in the crown 😲.



The crown/stem is in two parts so the spring and washer have to be pushed in so the stem can be removed and then we can access the crown seal and pull it out.



Now we can fit a new crown seal (after lubricating with silicone grease). All done.



A fixture is needed to hold the crown and re-fit the stem. I used my lathe chuck mounted to a wood block.

With the case assembled and the freshly restored crown/stem fitted it was time for a pressure test, So off to the kitchen. The watch case is placed in water in a vacuum container, a good vacuum pumped out (as much as I could manage) and the case checked for bubbles.

Success! No bubbles!



The vacuum is released and the watch sits in the water for about five minutes to allow atmospheric pressure to force water into the case.
It's too cold outside today to sit the watch in the sun to warm it, so the case is warmed to 45ºC in one of my drying units (an incandescent 10W pilot globe and some old bean cans).



Out of the warmer and a drop of ice cold water is put onto the crystal and left for 10 seconds and quickly wiped away. If a condensation spot is seen under the crystal it means that water has penetrated.
In this case, success! No condensation!



Part one finished, I can investigate the issue with the movement and service it as well.

Actual time?

About 4 to 6 hours, depending on problems or glitches.

However, total time can get pushed out due to other interruptions, e.g.: life, gardening, shopping, searching for parts, waiting for parts, many other little things that get in the way.

The last one (on a Tudor 390.......shudder) took about three months from receipt to return in real time.

The movement has now been stripped and is ready for cleaning.

All the parts laid out.



I had an idea of what was causing the setting problem so I checked the setting components, and sure enough here is the problem.



The clutch wheel has been severely worn down. After all the parts were cleaned I had another look and compared it to a clutch wheel from a different Seiko. A view from the top.



You can see how badly it's worn, the difference is obvious when looking at them together from the side.



So how does this happen? Possibly a design fault, or incorrect assembly at some time.

I found out that others have had similar issues with this movement, see this example where Martin had a problem with the setting mechanism. Although slightly different, it points to a latent defect with this setup (IMO).

Here's an explanatory pic I borrowed from Martin's blog. It shows a small pillar (my pointers in blue) on the end of the setting wheel lever, this is held down by the date wheel plate so it is meant to stop the setting wheel lever from riding up when the clutch wheel is engaged and turning, but there is too much clearance between the top of the pillar and the date wheel plate. This allows the assembly to lift, thereby partially disengaging the clutch wheel and causing wear. As the wear increases, the twisting force of the worn teeth cause the clutch lever to jump over the teeth of the setting wheel.



Solution?

A new Clutch Wheel (the setting wheel is OK). I'll have a look through my parts as this one is used in a large number of Seiko movements.

If I don't have one, the search will begin. But I'm getting used to that 😁.

Oh how I love the variations on eBay 🙄.

Still working with what looks like a ding in the coil? Lucky!

Yeah, worried me when I saw it but luckily it was hit with a "blunt object" I suspect, no wires cut or broken. There's another small ding just to the left of centre, and again, no breaks.

Long time no update.

The good news.
The owner sourced a new setting lever assy and clutch wheel from Cousins in the UK, and after a voyage slightly shorter then the First Fleet they arrived.

The Bad News. 😡
He ordered a setting lever for a Seiko 6309, not a 7548.

The Good News, Evening Edition. 😎
It appears that the setting lever assy, like many other parts, are based on the 6309, so although it has a slightly different part number, it is identical in form, fit and function.

So where are we?

The new parts were inspected then test fitted, then removed, lubricated, installed and checked with the complete watch in running/adjusting modes.

Everything is now working like new and the watch is undergoing a timing check for the next few days.
Sorry, no pics at the moment, been too busy with other projects but I'll post a shot tomorrow if anybody wants to see the completed project.

😉

Cheers

Jim

As a final action on this one, a picture.