Seiko 7A38 - by the numbers

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Forum Home > Bend it, Mend it - Mods & Wreckers > Phil's First mod - Crystal Clear Case-back

Phil
Member
Posts: 145

Here is my crystal case-back I've had made from an old case-back. It was just for my own amusement and I think it's turned out pretty good. The outside dia. is 29mm and I've left a 1/2mm lip on the inside of the case to seat the crystal on giving a viewing window of 28mm; the 1/2mm lip is around a 1/4mm thick and the flat crystal used is around 3/4mm thick standing slightly proud of the case. The crystal is 29.1mm dia and slotted in first time. Here's some pics.



Regards Phil


October 13, 2014 at 8:35 AM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 8884


That's pretty damned good, Phil. What a brilliant idea. I may just have to copy it. :P

October 13, 2014 at 8:49 AM Flag Quote & Reply

Phil
Member
Posts: 145

Thanks Paul, case-back's a bit rough but it's all I had I may polish it up later.

October 13, 2014 at 8:57 AM Flag Quote & Reply

nova
Member
Posts: 109

Nice +1

This is a great idea.

Is it possible to order one from you?

This could be used for a mod with blued screws :P

October 13, 2014 at 10:37 AM Flag Quote & Reply

Phil
Member
Posts: 145

Thanks Nova, the problem is that you would have to supply your own case backs, I used one off an old 7a38 as the case back for the one pictured is for a reasonably rare 7a28-710a and I didn't want use that. In truth as it was a one off it cost me around £40 but if there are a few of you that are interested and can send your case backs to me (say a batch of 10 or so) I could hopefully get them done for around £20/25 + postage.

I didn't think of blue screws or you could actually have pretty much most colours I think that would look pretty good

I'll see if there is anymore interest

ATB Phil

October 13, 2014 at 10:55 AM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 8884

I think it was Simon (Sir Alan) who first raised the question about (the lack of) display case-backs on 7Axx's when he wrote this:


Paul, I'm assuming from what I've read so far that the movement inside these is a normal 7Axx movement, but with the back-plate, battery positive plate (and possibly other plates?) and the centre seconds bridge anodised gold.

A rather cosmetic 'improvement' and rather pointless given the movement is hidden. :roll:


.... in the original Jean Lassale Thalassa thread (about halfway down the page). At that point in the thread, I'd just posted a couple of photos of the Seiko Lassale 7A54A and Jean Lassale Thalassa 7A74A movements (the first I'd seen of the latter), both of which are gold anodised. It certainly never dawned on me then to 'mod' the case-backs of either of these watches - even though with hindsight, the 7A54-7009 pocket watch is eminently do-able. If and when I decide to have one of these done, it'll be for something else ....


October 13, 2014 at 2:08 PM Flag Quote & Reply

Phil
Member
Posts: 145

Ok, I just sorted a few spare parts & screws out, bagged them up ready to take to the anodisers tomorrow. I shall report back on Mod 2 feasibility and cost to pretty up inside my crystal case back. Mr Nova has started me thinking (not always a good sign). :D

October 13, 2014 at 3:16 PM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 8884

Phil. Reference your: The crystal is 29.1mm dia and slotted in first time.

Do we assume the crystal is held in by tension fit, using a (clear) nylon crystal gasket ?


What I'm thinking about is 'bigging up' your idea slightly - by just a millimetre or so. You also wrote:

The outside dia. is 29mm and I've left a 1/2mm lip on the inside of the case to seat the crystal on giving a viewing window of 28mm.


A 7Axx movement back-plate is a shade under 29mm ∅ (actually 28.8mm) - which is why the extreme edges of yours are hidden.

Presuming Alex could do it, how about a 30mm crystal and glueing it in ? - which would give a 'full-size' viewing window of 29mm.


October 13, 2014 at 7:16 PM Flag Quote & Reply

Phil
Member
Posts: 145

No gasket Paul the crystal is just a pressure fit, I do have another spare case back that I shall get my man to do at 30mm with again a 1/2mm lip to give a 29mm viewing window and I'll see how that comes out. As Paul has alluded to and I didn't take to much notice of as it was just a bit of fun I do not believe my cut out is completely centre, it is what we used to call half a titty out, not hugely noticable in real size but as I know in the watch world it has to be bang on or it doesn't count. I shall take some more pics when I can. I am not going to pop the crystal out to measure but  eagle eyed Paul is definitely right it is "half a titty out", I shall just have my other one done and point out the shabby job he did last time. Please bear with me for this info as I will try and get the method used.

Thanks Phil

October 14, 2014 at 11:03 AM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 8884

Phil. Per my PM, if you do decide to go for the 'full monty' using a 30mm crystal, the cut-out will need to be spot on dead centre. ;)

October 14, 2014 at 11:13 AM Flag Quote & Reply

Phil
Member
Posts: 145

Ok here's another shot as you can see, the 1/2mm lip where my tweezers are placed and below is less than the opposite side :mad:


October 14, 2014 at 12:03 PM Flag Quote & Reply

Phil
Member
Posts: 145

Right, my 2nd one has been done to 30mm - 29mm viewing window, this proved to be much harder to do than my previous one as Paul alluded too as there is less material to work with 

It's turned out pretty good and it's bang on central, however if you turn it around and look from the inside out (I know, who's going to be bothered) not quite so good

and from the front

and what you can now see combined with my 2nd mod 

Yes Paul I will change it to a 28 when I have time :P

All in all a worthwhile restoration and mod (or two really) to make my watch unique and for the purists it is reversable. I do not think I will ever sell this watch, it's a keeper for me

Hope you enjoyed it

Thanks Phil


November 1, 2014 at 8:08 AM Flag Quote & Reply

garacs1
Member
Posts: 508

Phil, it turned out really great! One thing turns me off, though: the battery. Sorry this is something I would not like to see at all in a watch back, but it's just me being really picky.

--

My personal Blog: www.onlyvintagewatches.com/blog

November 5, 2014 at 3:43 AM Flag Quote & Reply

Phil
Member
Posts: 145

No problem George, I can't do much about that :P

November 5, 2014 at 11:10 AM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 8884

Might look a little better if the stampings on the battery were aligned with those on the back-plate and battery positive plate. ;)

But that's just me being really picky. :P

November 5, 2014 at 1:32 PM Flag Quote & Reply

Phil
Member
Posts: 145

Picky, picky, picky :roll: :lol:


November 6, 2014 at 10:04 AM Flag Quote & Reply

donwatch
Member
Posts: 504

Another thought --won't uv light filter in and cause damage to the pc board ?  Paul any thoughts ?  Or is the board sheltered enough ?   I like the idea  ;)  nice tidy job 8)

November 6, 2014 at 11:15 AM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 8884

It's only the CMOS IC on the PCB that is affected by UV, Don.  It's well covered by the anti-magnetic backplate anyway. Presumably, most of the time, Phil's display case-back should be against his wrist - so unless he inadvertently leaves the watch lying face-down in direct sunlight, with the watch pointing in the exact direction - I think the risk of any damage is minimal.

November 6, 2014 at 11:30 AM Flag Quote & Reply

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