Seiko 7A38 - by the numbers

Subtitle

Forums

Post Reply
Forum Home > Bend it, Mend it - Mods & Wreckers > A brief exercise in fettling a 7A38 'Dinky Diver'

Seiko7A38
Site Owner
Posts: 12355

Last month I bought a JDM 7A38-6040 off Yahoo Japan. Or should I more correctly say forum member Daisuke kindly proxy bid on it on my behalf. It's a model that had been missing from my collection for some considerable time. I've missed out on a number of what were probably far better examples over the years. Anyway 'we' won this auction. It didn't look too bad in the seller's photos (apart from the bezel insert).



Before Daisuke started bidding on the auction, one thing we'd discussed, that had concerned me, was the diagonal scratch to the top right of the 30 minute counting sub-dial. It was difficult to discern whether it was a mark on the crystal or on the dial. Turns out that was the least of my worries. :roll:


On 30th March, Daisuke emailed me, his message included:


Tonight, in Japan, I received your 7A38-6040 and checked it. Here's the details.

This watch is completely junk, all pushers are fixed not work, but bezel rotation is smooth. The scratch which you were worried about, that's on glass. The dial and index plus hands are all visually clean.


April 30, 2018 at 6:30 AM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 12355

Here's a partial copy and paste of my post in the WRUW thread dated 6th April:


Once fitted with a new battery, given a little persuasion, it runs - and the bracelet comfortably fits my wrist on the last pair of clasp adjustment holes. So it's a start; I've finally got one - even if it needs a little TLC. 



April 30, 2018 at 6:48 AM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 12355

I suppose I should expand on that 'given a little persuasion'. 




When I first fitted the replacement battery, it didn't immediately spring into life. :( What Daisuke had written about the pusher buttons being 'fixed' was correct - they were absolutely solid !! I had to remove the dial / movement from the watch case to carefully nudge the chrono' hands round to their 'Zero' positions for the wrist shot.


At that stage, I didn't risk attempting to operate the chrono' function using the cams of the actuator levers, because I wasn't sure how bad the rust was. My main concern was whether the watch would actually keep running and good time.


April 30, 2018 at 7:08 AM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 12355

Once I'd established it did, I started stripping it down - obviously the first thing to do was to free off the seized pushers ....




The 2 o'clock pusher moved as soon as I removed the circlip. The 10 o'clock pusher came out after a few squirts of WD-40 and gently easing back and forth, a fraction of a millimetre at a time. But the 4 o'clock pusher remained obstinately stuck in place. :mad: The above photo shows the case before I started drenching it in WD-40. The remains of the 4 o'clock pusher's rusted circlip still on the crystal.


Eventually after a few days literally soaking in WD-40, the 4 o'clock pusher finally succumbed - without me having to resort to using brute force (or my mini G-clamp).




As usual, it was a combination of dirt, rust and a badly distorted O-ring seal that was holding it so firmly in place. Note how soaked with WD-40 everything was at this stage - hence the layers of kitchen paper towel. :roll:


Once I'd degreased, cleaned and dried the watch case, I popped the movement back in, to do a partial strip-down in situ. Note I deliberately hadn't replaced the pushers at this stage.



Turns out the rock-solid pusher O-ring seals had actually done a half decent job. There was some surface rust on the cam of the 10 o'clock pusher's actuator lever and no great surprise, the 4 o'clock pusher was worse, but nothing like I'd feared.



There was just a trace of rust evident on the underside of the anti-magnetic plate, corresponding to the position of the 4 o'clock pusher. Both the rusted cams of the two affected switch actuator levers were given a light rotary wire brushing, polished up with Wet & Dry paper, then given a quick spray of WD-40, left to dry and were subsequently re-used.


April 30, 2018 at 7:29 AM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 12355

Yesterday I finally got round to reassembling the watch. Here's the head, fitted with a replacement genuine Seiko p/n 285W26GN00 crystal.




I'd removed the bezel before I started tackling the pushers. Here it is stripped and cleaned, but with the 0.10mm stainless steel shim still glued to the insert.



As yet there's no source of decent repro' bezel inserts in this size, so I 'borrowed' a genuine Seiko insert from this NOS 7A38-6010 bezel, which I'd bought some time ago and fortunately had no prior need of (as a direct replacement).



I'm sure I'd taken a photo of the watch head with the bezel re-fitted, but it appears I've inadvertently deleted it from my camera, before I'd downloaded it to my PC. :roll:


Had I been able to post it, I wanted to use it to illustrate a little tip. In situations like this, where the bezel shell and insert are separate, it pays to re-fit the bezel shell to the case first. The click-ball will determine the resting place of the bezel. The replacement insert will not necessarily align perfectly with the bezel knurling. But what you do want to ensure is that the inverted triangle / pip aligns perfectly with the dial's 12 o'clock mark. Hence the logic in fitting the insert afterwards. ;)


Here's the 'after' wristshot I posted in the WRUW thread yesterday afternoon:




The moral of the story (which is not lost on me) being: Buy the best example you can afford (rather than settling for a 'stop-gap').


April 30, 2018 at 8:30 AM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 12355

I'd debated whether it was actually worth bothering to keep on looking for a better 7A38-6040 on Yahoo Japan - particularly as how their selling prices had increased over the last year or so. Plus there'd been a couple of nice examples I'd missed out on, for not being willing to pay more than 60,000 Yen at the time. I was almost content with my restored 'beater' - apart from one thing: its tired bracelet. I'd written in an earlier post (on 30th April - copied from the WRUW thread):


.... the bracelet comfortably fits my wrist on the last pair of clasp adjustment holes.


That wasn't strictly correct. Precariously would have been a better word than comfortably. Yes, it fitted my wrist, but only by dint of the excessive amount of stretch due to wear / slop between the links. :/ A couple of weeks ago, a decent looking used YA29A bracelet (minus end pieces) came up on Yahoo Japan. I asked Daisuke if he'd bid on it for me - as ever he kindly obliged and we won. :D



Daisuke's package containing the YA29A bracelet arrived in the morning post. :)

I haven't fitted it yet. It's a little bit shiny. I may decide to give it a light re-brushing to tone it down a bit. One thing's for sure, it may be secondhand, but it's a LOT better than my existing bracelet. Here they are below, side-by-side, with the newer YA29A bracelet at the top. That has one more removable adjustment link than my old bracelet - and it's actually shorter ! :o I haven't pulled the old one out fully, to show the complete extent of the stretching / wear, but you can see the gaps between some of the links.



December 15, 2018 at 8:32 AM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 12355

After some deliberation, I decided to fit that newer YA29A bracelet 'as is', without refinishing it. It may be a little too shiny, but it matches the watch head well in that respect. Here's a different wrist shot to the one I just posted in the WRUW thread.




The bracelet may not look that different to its predecessor, but it gives me much more confidence (to be able to actually wear the watch, without fear of it breaking). Here's a shot of the underside of the 'new' bracelet showing minimal slop - even between the adjustment links. :)



January 3, 2019 at 8:57 AM Flag Quote & Reply

You must login to post.