Seiko 7A38 - by the numbers

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Forum Home > Parts Info, Tech Tips and Tinkering > Installing crystal

Licu
Member
Posts: 40

Hi,


I have a 7A28-702A which has the crystal pretty scratched. I know that you are recommending the Sternkreuz crystals. Where can I get one (shipped to my location, Romania EU)?

I also saw this one on the ebay, is this any good:

http://www.ebay.com/itm/281129659993


Do I also need to purchase a gasket for it? Or is the old one remaining in place?


I've talked with a watch repair guy here which seems pretty handy, he said that he can change it. Is there any risk when doing this (damage to the movement)?


Many thanks,

Adrian

December 1, 2013 at 1:29 PM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 14136

Adrian.

In the UK, we get Sternkreuz crystals from Cousins UK. Athough they are a wholesaler, they will actually deal with individuals direct.

As you've probably gathered from our various posts, Simon and I would both recommend using Sternkreuz p/n XMF320.927.

You can re-use your existing crystal gasket if it isn't damaged. Besides, it's difficult to fit a replacement crystal with a new gasket.

There is NO RISK to the dial and movement when replacing a crystal, because they will already be removed from the watch case.

The only risk is to the plastic Tachymeter dial ring - if someone is careless and picks up the wrong diameter crystal press die.

I suspect that's what happened to the Tachymeter ring in this 7A38-7029: http://www.ebay.co.uk/itm/221327749088

December 1, 2013 at 2:44 PM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 14136

I wrote about that minor hazard recently. See my last post in this thread: http://www.seiko7a38.com/apps/forums/topics/show/7168318


One thing I'd like to reiterate, though, is that it isn't necessary to remove the (fixed) bezel used on these style of 'normal' Seiko 7Axx's when replacing a scratched crystal. Indeed, I'd advise against disturbing the nylon bezel to case gasket unless absolutely neccesary, because they can sometimes be a pig to re-fit. You simply press out the old crystal from inside the watch case, but making sure that you select a nylon die small enough (usually <24mm / 25mm Ø) that will pass safely through the plastic Tachymeter / Minute ring.



December 1, 2013 at 5:10 PM Flag Quote & Reply

Licu
Member
Posts: 40

Hi,


Thank you for all the info. So, just to be sure, the crystal Sternkreuz p/n XMF320.927 is the one to get for my model (7A28-702A)?


I will also talk with my watch repair guy to make sure he is up to the task. I think I remember there are some small tricks to get the movement out (something related to the crown?).


Kind Regards,

Adrian

--


December 2, 2013 at 5:30 AM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 14136

It's the closest substitute in terms of appearance / dimensions to Seiko p/n 320W40GN00 which is obsolete and no longer available.


There's no 'trick' to removing a 7Axx movement from a watch case - you simply pull the crown out to the second position and depress the release lever, which is clearly marked <-- PUSH. The only precaution I take is to set all the hands to '12' / zero before removing it.

December 2, 2013 at 5:46 AM Flag Quote & Reply

Rob Benham
Member
Posts: 281

Oh, gosh.  I wish I'd joined this forum a few days earlier.  My 7A38 7000 crystal surround is lying on the bench in a trial run to see how hard it is to get it back when the new crystal is fitted.  I have no special equipment, but pressing the case onto the lens while it was lying on soft cotton cloth seemed to get it back okay.  It took all the force my thumbs could provide.

Frankly, given the screw back, I was surprised to find the front so 'cheaply' pressed on.  It seems to go from Rolex to Timex across the thickness of the watch.

Having suffered a Texas repair (shop had a Seiko sign over it.) I really lost interest in the watch after that, but now I'm rather keen to bring it at least half way back to its original state. 

December 4, 2013 at 1:59 PM Flag Quote & Reply

Rob Benham
Member
Posts: 281


Having 'won' on eeeee-bay a gold plated version of my 7A38-7000, I set about trying to destroy it with a new cack-handedness obviously acquired with advancing years and excessive vino.  I was a one man demolition squad, launching into tasks as though I'd still got the hands and indeed, eyes, of someone that fettled fusee movements without the aid of specs.  (didn't do much.  Just attached the chain on the drum and away it went.) 

This morning, I went to bed c 05:00 after looking at photo after photo of watch-fettling on this site.  Got tired, but propped me eyes open with matches and reentered the world of rusted-out batteries and damaged circuit boards.  Fascinating.  Put in an order for tools and parts from an American supplier.  I had failed to find a local supplier for Sternkreuz.   However, a Radio Shack battery at $6.99 translated to 99 cents - and by a known maker.  (one that breeds rabbits.)  The crystal lenses were $2.99   I ordered a couple of 32.5 X 1.5 beveled, and one 32.4, to hedge my bets.  I don't expect too much at that price, but I need to hone my skills on low value parts.

I noticed they sold a lens polishing wax.  I'd already broken my (gold watch) lens getting it out, but since it was beveled and the myriad scratches were not deep, I might have had a bash at polishing them out.  My frustration increased when I found it had a small bevel on the inside - to aid insertion.  I'd learned from this site this perhaps indicates a Seiko original crystal and its thickness would have allowed polishing without touching the bezel.  Academic now. :(

What I have learned is that the gold is very, very delicate.  In a moment of madness . . . no, two moments of madness, I managed to mark it twice.  Once getting the bezel off and again straightening a kinked link.  The frustrating thing is, I got the link almost perfect, but then marked it just to one side of the target area.  It's not bad, but I know it's there.

Getting the circlips off.  By the second watch I was forearmed.  I copied Paul's homemade device - but to cover all bases, not only dabbed on a touch of silicone, but covered the entire job in a foot square sheet of shrink-wrap.  At first, I tried to do it laparoscopically.  It was okay, but then I wondered why I was puggling inside.  I then simply probed down onto the plastic - with a much clearer view - and they popped off easily.  The one that did escape the main blob, carried enough silicone on its travels to stick itself to the surface just 20mm away.  They are still stuck to the paper under the dust cover - a piece of Tupperware that hasn't been missed yet.

I am apprehensive about the refitting.  One tutorial shows the fitting of the lens into the bezel while it's removed.  That seems okay if one is mindful of the delicacy of the ring, but it takes quite a pressure to fit the bezel onto the watch body.  I'm not at all sure I want to press on even a bedded-in lens as hard as that and I doubt my concave press dies will remain clear of the glass.  I'll see when they arrive.  The one really difficult issue is getting the Tacho ring between the bezel and the body.  That small plastic ring, with its minute numbers, really ups the anti.  Time over again, and if needs be, I'd turn a die to the right diameter to just clear the plastic Tachy ring.  Oh, for my old workshop with its Myford lathe. 

I'm going to need to seek your advice about lubing the O rings/seals.  And is there an argument for honing the sharp edge off the inner edge?  Silicone would perhaps see the lens escaping some time in the not too distant  future, and water, well, these watches seem to be a bit of a water magnet.  A hint of spittle is nothing short of magic in some cases, but . . . oh, two puns in one sentence.  Time for bed.   Photos when the kit arrives.


December 20, 2013 at 12:10 AM Flag Quote & Reply

Rob Benham
Member
Posts: 281

Re the gold plated 7A38-7000

Well, the parts and 'tools' arrived, but I opened them about midnight.  The screwdrivers were what one would expect for a base set.  $6-ish.  The smallest one was ground some 30 degrees off.  However, one gets a spare set of tips.

The batteries were as described and the washers - the flat type - seem perfect, though I've yet to really tighten one. 

The lenses are beveled both sides, the lead-in very small.  I was relieved to see that. 

I tried to 'start' one lens.  After three goes it was going in level, but this was only a test and I wanted it out again.  I only pressed by hand with strong plastic between the nylon die and the glass.  I couldn't quite trust that hard material to leave the glass perfect.  I popped the lens out again and tried the undersize one.

32.4 X 1.5  It went in all too easily, but looked good. (As mentioned, my first watch was once fitted with I'd guess a 1.0 mm glass and looked very poor.  Such a cosmetic difference.   It really did pop out with unnearving ease.  What a difference .1mm makes.


Now the questions:   Is there anything to lube the seals with that will not cause them to come asunder later? *   Right now, I'm thinking I'll warm the bezel and cool the crystal.  Then be quick. :roll:  Yeh, right.  Speed I'm thinking will be the catalyst for disaster.  However, I am mindful to put the glass in first, because should it fracture, I imagine shards of glass hurting the Tachyo. ring.  I'd wondered about putting cotton wool in front of its face edge, but it would all be getting a bit complicated and sure as eggs strands of it would get trapped in something.

Pushing the bezel on while the glass is in situ.  A bit unnerving as well, but I find one of the dies will clear the crystal while putting pressure on the bezel.  I'm really not sure. 

So, does anyone put pressure on the crystal to put the bezel on?

And does anyone lube with some magic product that later grips?  (sorry if that's been discussed, I thought I'd seen it mentioned, but if I did, I can't find it.

December 24, 2013 at 3:45 AM Flag Quote & Reply

Sir Alan
Member
Posts: 458

My self learned tips:


1 - its a lot easier than it looks, don't overthink it

2 - get the correct diameter crystal. Exactly. Not close.

3 - you don't need any lube on crystal or bezel gaskets

4 - a crystal that is thicker than the original works, but be careful not to push it too far in (it is likely to crack)

5 - don't push domed crystal in with a flat die

6 - pushing bezels in is very easy - you can push either the glass or the bezel itself

7 - only use nylon dies

8 - use the widest die possible when pushing a crystal in

9 - be very careful when pushing crystals out, watch out for the tachy ring



December 24, 2013 at 4:27 AM Flag Quote & Reply

Rob Benham
Member
Posts: 281

Thanks for that.  Yes, I usually do overthink things, however, in heavier engineering pushing past dry O rings is often a disaster. 

I did tidy the post up and write a bit more - something about repeated changes of cabin pressure in aircraft and the loading on the crystal, but it seems if the edit time runs out during an edit, all is lost.  I did say something about Bah, humbug - Christmas is getting in the way of my fettling, but managed to add, merry Christmas, everyone. :D


Merged from other thread (posted on 28/12/2013):


Re my newly acquired gold plated  7A38-7000 

Crystal fitted and trying to figure out how to clean the glass in situ now that I’ve had to fettle the pusher.  I’d put tissue in the watch but even then the glass is no longer perfect.   I need a glass equivalent of that blue putty I see used on this forum. 

Re my original stainless 7A38-7000

As per Paul’s suggestion in one of the posts, I selected a die with the thickest part able to pass through the tachy ring.   The largest cupped die I have touches about half way down the bezel.   I repaired to the garage and used my drill press. 

I used both hands on the bars to gain detailed control and took a deep breath.  The old lens popped out with quite a noise but intact.   I didn’t breath until I’d inspected that precious plastic ring.

As suspected, the Seiko dealer in San Antonio all those years ago had fitted a 1mm crystal.   Now, a strange thing.   While calling local watchmakers (think of Mexico and back street America combined) I happened across an old guy who only had plastic lenses.   He phoned me sometime later and said he’d found a 2mm lens crystal, which I declined as new ones were on their way.  Now, thinking about it, another half mill might just give a more chunky appearance.   Given the bevel is sufficient to give a good cosmetic appearance, are there any pitfalls about it staying put?  It seems to me that the seal is seeing a flat surface on the upper edge anyway.  (which is more than can be said for the crystal that came out.)


December 24, 2013 at 10:28 AM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 14136

Rob. You can use Rodico (that blue putty as you call it) to clean inside the crystal. It works on glass as well as other materials. ;)

December 29, 2013 at 5:44 AM Flag Quote & Reply

Rob Benham
Member
Posts: 281

Thanks, I shall add that to my shipable collection.  Small purchases only since It's going to cost to get stuff home.

Back to that Texas repair man/botcher with the Seiko sign over his shop.  Close inspection tonight revealed something on the seal.  My guess is, to add to his sins, he used an adhesive. :mad:  It does not bode well for cleaning.

I'm now having to search for an American supplier, or remove this one and try various chemicals to get it back to the plastic/rubber.  Any advice on honing in on the right part would be appreciated. 


December 29, 2013 at 11:28 PM Flag Quote & Reply

Rob Benham
Member
Posts: 281

That should have been, homing in on the right part, of course. 

However, I've been re-reading Paul's post on starting the crystal when a new seal has been fitted.  As a newbie, I'm concerned I won't be able to do that.  Since there is clearly some 'product' on the nylon? ring it dawned on me to also use a trace of adhesive and fit the undersized crystal I purchased for learning.  This should tide me over until I'm more settled and can start collecting a few tools/spares.  In a very sad storeage unit in the UK, I even have a wonderful old Whatson Scientific microscope.  Such visual aids are becoming more important these days. :/

December 30, 2013 at 1:20 PM Flag Quote & Reply

MTX371
Member
Posts: 46

Morning Forum,

I have a little collection of 7A28/38/48.
On some of these watches I want to replace the crystals.
Do I mandatory need a pressing tool for this work?
Is there any kind of tutorial available (anywhere in the web)?

Are the crystals of the 7A28/38/48 all the same size (e.g. 31mm x 1,5mm) or do the crystals differ from watch to watch? If they would be all the same size I could order all the crystals at once and wouldn´t have to measure every crystals and order them separately...

Best regards,
Tim


January 3, 2014 at 5:40 AM Flag Quote & Reply

Sir Alan
Member
Posts: 458

Hi Tim,


it looks like you are setting off on a well trodden path :)


I suggest reading this:


http://www.seiko7a38.com/apps/forums/topics/show/7187327-crystals-and-gaskets


and then doing some general googling on this subject. There are lots of threads on this topic out there on the various watch forums and blog sites.


In my opinion, yes you do need a press. They aren't expensive and it will pay for itself many times over.


In this thread you'll see the tools I purchased, along with the type of press:


http://www.seiko7a38.com/apps/forums/topics/show/7168318-essential-tools


January 3, 2014 at 5:54 AM Flag Quote & Reply

Rob Benham
Member
Posts: 281

Re my SS 7A38-7000 that I've owned from new.

Well, I resisted the tmptation to use an adhesive with the undersized glass and spent ages cleaning the existing gasket.  I just couldn't risk the tachy ring so took off the bezel yet again.* After a while and some chemistry, it seemed clear of adhesive and I pressed in the full sized crystal. (again using my drill press with proper dies.  It took some time before I was satisfied it was inserted precisely into the bezel, but finally it seemed exactly true.  However, it is not the final offering, because the gasket allowed particles of material to be carried with the (inner beveled) glass.  Drat.  It takes an eyeglass to see the debris, but I know it's there - trapped against the fine 'horizontal' case surface.  5 or 6 specs, but infuriatingl..  I made a tool from a large needle to try to chisel them away - sharp flat end tilted at 30 degrees.  It didn't work. 

However, I'm going to have to do it again properly one day, when I lay hands on a correct gasket.  I'll do the pusher O rings at the same time.

I like the flat back gasket, it seems good mechanics when used with silicone**, but the purist probably will not want to see a black line however thin.


*The bezel has now been off 3 times.  It really does seem to go on firmly, and is hard to get off, but I'm begining to feel a bit uneasy about the (white) gasket.  Any opinions about the number of times one can remove this?

** The silicone advertised in tiny pots seems expensive.  Is the electronics silicone in a tube quite out of the question?

Oh, and does anyone lube with two different oils when doing a major overhaul?  Mobius oil.  What makes that different?

January 5, 2014 at 1:30 AM Flag Quote & Reply

MTX371
Member
Posts: 46

Sir Alan at January 3, 2014 at 5:54 AM

Hi Tim,


it looks like you are setting off on a well trodden path :)


I suggest reading this:


http://www.seiko7a38.com/apps/forums/topics/show/7187327-crystals-and-gaskets


and then doing some general googling on this subject. There are lots of threads on this topic out there on the various watch forums and blog sites.


In my opinion, yes you do need a press. They aren't expensive and it will pay for itself many times over.


In this thread you'll see the tools I purchased, along with the type of press:


http://www.seiko7a38.com/apps/forums/topics/show/7168318-essential-tools


Hi guys,

read the threads already some time ago... I am an absolute beginner, but already have some tools for working on the beauties... As it seems I need a press now and some other things to service my babies...

If I understand right the crystals from the 7A28/38/48 differ quite a lot - different watches, different crystals...

I tried to make a little list of my "projects" (where the crystals have to be replaced) and would like to know from you guys, if this is right and if I can order the crystals (most likely at Cousins).


Cheers!

Tim 

January 5, 2014 at 8:08 AM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 14136

Sorry Tim. I can't see your "projects" list (if that's what was embedded in your post). Tried to sort out your link for you, but couldn't. :(


One thing I know it's a .tiff file which is an ancient format that hardly anybody uses / supports nowadays. Far better to use .jpg or .png.


The fact that you're trying to hide the URL doesn't help: http://webkit-fake-url://4015F175-4BD6-4C09-8251-42FBEC5419B8/image.tiff 

January 5, 2014 at 9:44 AM Flag Quote & Reply

MTX371
Member
Posts: 46
Sorry - isn´t it possible to upload an image from hard disk?

NAME ORIGINAL-NO. SUBSTITUTE (Sternkreuz)
7A28-702A 320W40GN00 XMF320.927
7A38-6080 300WD6GN00 XMF300.860
 -7020 310W62GN00 XMF310.925
 -7060 320W40GN00 XMF320.927
 -7090 285W24GN00 ?
 -7120 290W38GN00 ?
 -7130 290W38GN00 ?
 -7190 310W62GN00 XMF310.925
 -7280 310W62JN01 XMF310.925 ?
7A48-5010 310W62GN00 XMF310.925

January 5, 2014 at 2:47 PM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 14136

It appears not, Tim. For embedding images in a post, unless it's a file hosted on this domain (which only I, as site owner, can do) it's usual for forum members to use some kind of remote image hosting site, like Photobucket (easiest to use).

See: http://www.seiko7a38.com/apps/forums/topics/show/7208345-how-to-upload-a-photo-to-this-forum-


I'm just checking through your list. Give me 5 minutes or so. ;)


For the 7A38-7020, Sternkreuz p/n XMF310.925 is O.K., but you could just as easily use the cheaper MSM310.

For the 7A28-7090, I'd personally use a Sternkreuz p/n MSM285 but you could use Cousins own p/n F150CMH285.

For the 7A38-7120 and 7A38-7130 you could use Sternkreuz p/n MSM290 or again Cousins own p/n F150CMH290.

For the 7A38-7190 and 7A38-7280, again it isn't really neccessary to go to the expense of using a XMF310.925 as replacement.

I've always used Sternkreuz p/n MSM310 with plain straight-sided edges - and there's the much cheaper Cousins p/n F150CMH310.

Same applies to the 7A48-5010 - again it depends if you want a fancy ground polished edge, which the original crystal doesn't have.


January 5, 2014 at 3:14 PM Flag Quote & Reply

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