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Discussion Starter · #1 ·
have never taken apart a 8900 before but have one that im prepping for incoming resin which needed a very good clean so i took off the bezel ring and noticed theres a little spring in the 4 oclock position. anyone know if its for something important or is it just an earth? :think:

 

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Since this spring is not connected to the module, it has absolutely no electrical functions.

From my experience with the 8900, the spring serves the purpose of a bumper for the metal bezel. This had to be devised since the resin of the 8900 bezel does not cover as much of the face as it does in other watches like the 6900, due to the presence of the metallic bezel ring.

It goes without saying that the ring is the most vulnerable impact area on a 8900 so it couldn't be hard-fixed on the resin case. This spring on the 8900 serves a dual purpose

- provides the metal bezel ring with some shock absorption against day to day dings
- prevents bumps from propagating from the metal bezel to the case. (the shocks which, otherwise would have been absorbed by the resin bezel)

To understand this better, mount the metal insert back on the case, not mounting the resin bezel. Press down on the metal insert and you can observe the action of the spring, providing cushioning between the case and the metal insert.

Hope that answers!

PS: From Mike's links, apparently every G with a metallic bezel insert has a spring under the metal insert, which explains!
 

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touching metal = ground.
so a spring touching the metal bezel = ground.
logically a spring at one corner offering supposedly shock protection can really only be effective in that one corner.
Point to ponder: what exactly are you trying to ground, why, and why only in watches with a metallic bezel insert, why not on a 5000 or a frog?
 

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Point to ponder: what exactly are you trying to ground, why, and why only in watches with a metallic bezel insert, why not on a 5000 or a frog?
all gshocks have a spring, or some form of ground.
almost all have it on the back of the module touching the caseback.
its anyones guess why its on the front of the 8900, perhaps a diff module design.

digging abit more, the spring also serves as some form of circuit completion for the speaker so as to have beeps etc.

this thread should answer ur question on the 5000 / frog.
https://www.watchuseek.com/f43/additional-tips-g-shock-battery-replacement-623055.html

* On 4 screw plate G-Shocks, the module will have a tiny spring on it. This makes contact with the piezo speaker on the case back, which is activated when the alarm goes off or when changing modes. On screw-back cases, there is no alarm spring but instead metal "prongs" that touch the piezo speaker.
btw, there are also wave ceptors with spring on the front.
 

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all gshocks have a spring, or some form of ground.
almost all have it on the back of the module touching the caseback.
its anyones guess why its on the front of the 8900, perhaps a diff module design.
The 8900 has that spring too, inside the case. If you look at this spring closely, you'd notice it's not connected to anything. It is just mounted between the resin case and the bezel ring. There is no circuit, no earth and no flow of electricity.

Second point to think of - any electrical connection outside the case is an exposed surface, which just doesn't make sense. What about when the watch is wet? The spring is completely exposed and will short out - defeating the purpose of any electrical connections it's supposed to be handling.

Third point - what if the the spring or the ring were to be dislodged on impact? Had they served some purpose like ground/electrical connection, an impact would knock the connection out, rendering some functionality useless. G-shock modules are designed to remain functional as long as the case is intact, so the possibility of an externally mounted vulnerability is completely improbable.

It just serves one simple purpose of shock absorption, since the metal ring is rigid, and if it were to be hard-fixed, any impact to the ring would directly propagate to the case, risking a damage to the case itself.

Ideally there should have been at least two such springs, mounted diagonally for best results but I guess one is better than none.
 

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Since this spring is not connected to the module, it has absolutely no electrical functions.
As you mentioned in post #8, for those springs to do a good job of shock absorption, there should be AT LEAST two springs, if not four, and the springs should be strong enough to actually DO some shock absorbing.

As it is, these springs are practically microscopic-- they're the size of the internal alarm springs -- so they're not really big enough to absorb any sort of significant shock.

In another thread (that I can't find right now) I'm 99% sure another member proved that the springs fit into holes which sit "outside" the rear O-ring, and connect the front bezel to the backplate. Thus, if there's static electricity when someone takes off a jacket, it's not going to jump from the jacket to the bezel and then THROUGH the module, which might short it out.

If you take a look at https://www.watchuseek.com/f43/how-change-ctl1616-rechargeable-battery-41076.html in the Articles and Tutorials section, there are several pictures of the inside of an MTG-900.

I borrowed one of the pictures from Jacobe, and added one of my own pictures of an MTG-M900 without the bezels:

Watch Diving equipment Dive computer Auto part Watch accessory


I can't explain why the spring isn't visible in the first picture, since I didn't take that watch apart, but it certainly LOOKS like the holes I highlighted do in fact go all the way through the case!

I mentioned losing the spring out of my MTG-M900 in my "Custom MTG-M900" thread as well, and had an interesting time replacing it. The first replacement spring I ordered from Pacparts was apparently an alarm spring, and was far too short -- when I dropped it into the hole it vanished completely, so I had to guess and order another spring with a different part number -- that one DID fit into the hole with some of its length sticking out, and I THINK it's contacting the back of the bezel now. Looking at another MTG-M900 I took apart, it looks as if there should be a small, "L" shaped metal piece that fits into the front of that spring, which then should touch the bezel.

The 8900 has that spring too, inside the case. If you look at this spring closely, you'd notice it's not connected to anything. It is just mounted between the resin case and the bezel ring. There is no circuit, no earth and no flow of electricity.

Second point to think of - any electrical connection outside the case is an exposed surface, which just doesn't make sense. What about when the watch is wet? The spring is completely exposed and will short out - defeating the purpose of any electrical connections it's supposed to be handling.

Third point - what if the the spring or the ring were to be dislodged on impact? Had they served some purpose like ground/electrical connection, an impact would knock the connection out, rendering some functionality useless. G-shock modules are designed to remain functional as long as the case is intact, so the possibility of an externally mounted vulnerability is completely improbable.
I can't speak for the 8900, but on the MTG-(M)900 and GW-(M)500 series, there's a small space on the inside of the plastic bezel where the metal bezel can make a connection.

If the spring gets wet, it's going to make an even BETTER connection between the metal bezel and the caseback!

The metal and plastic bezels fit together like puzzle pieces, and once they snap together they ARE "hard-fixed." Casio even uses double-sided tape to hold them together, but once those pieces are force-fit together and then snapped onto the case, they might as well be a solid piece of metal OR plastic. They will still absorb SOME shock, but no more than a solid resin bezel from a GW-6900.
 

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I'm 99% sure another member proved that the springs fit into holes which sit "outside" the rear O-ring, and connect the front bezel to the backplate.
I can't speak for the 8900, but on the MTG-(M)900 and GW-(M)500 series, there's a small space on the inside of the plastic bezel where the metal bezel can make a connection
I can confirm that's not the case on the 8900. Right now no pics with me, but once I get home I can pull out my dead 8900 and click some very clear closeups.

As it is, these springs are practically microscopic-- they're the size of the internal alarm springs -- so they're not really big enough to absorb any sort of significant shock.

Yes, that's what I thought too, when I opened up the 8900 and then I realized the spring just slots into a hole on the case and it keeps barely 1mm of travel between the ring and the case. Probably a better solution than having nothing at all. As I said previously, I will surely click a few proper closeups once I get back home, so that this mystery is solved for once and all!!!
 

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Thanks for your kind words 馃槉
 

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The 7700 & 7710 have the same single spring, but in the rear of the case kind of just under one of the lugs. These watches also have a metal inner bezel ring and when I asked the question on here when repairing one I was told it acted as a grounding spring as it was long enough to touch the bezel ring and backplate at the same time.
 

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Discussion Starter · #17 ·
thanks guys |>

now that mike mentioned i have seen the same spring on an old mtg and a few others. id have to say its looks like its only for earthing only tho, its a spring shape to compensate for any bending or flexing of the metal.

i did actually do the trampoline thing like you mentioned kmb but that was only after i removed all the adhesive. that adhesive is one of a few things that make me think the spring is not a shock absorber. it sticks a rubber gasket to the case and the gasket to the metal ring and sticks it down damn good. then you have the resin bezel on top of that so nothing there is going to move at all. for a spring to cushion impact it needs some kind of travel which doesnt happen when the ring sits flush with the case. if anything the gasket would probably be a shock absorber as well, just like the rubber inside the case.
 

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I borrowed one of the pictures from Jacobe, and added one of my own pictures of an MTG-M900 without the bezels:
View attachment 10045738
I will surely click a few proper closeups once I get back home, so that this mystery is solved for once and all!!!
Mystery still unsolved!

Here're a couple of pics of the spring I clicked earlier today. As you can see, there're no separate holes for the spring to make contact with the backplate (unlike the MTG900 pics which Mike posted, where there are two holes and two springs). And then the 2nd picture of the spring itself - it's not long enough to pass through the case and touch the backplate on the other side.

Yet another interesting question that pops up in my mind - why would you want the electricity to be transferred to the backplate which is in direct contact with your wrist? Imagine a situation when you working on some project and the metal ring touches an electrical connection. You'd get zapped!!!! Not having a connection is safer - the case will insulate the electricity and prevent it from propagating from your wrist. I am assuming the same for static electricity as well - why would you want the static from your sweatshirt being transferred to your wrist via your watch? Did Casio take the electrocuted cat on the Rangeman a bit too seriously?

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Here're a couple of pics of the spring I clicked earlier today. As you can see, there're no separate holes for the spring to make contact with the backplate (unlike the MTG900 pics which Mike posted, where there are two holes and two springs).
For whatever it's worth, there are two holes in each MTG-(M)900/GW-500 case, but having taken apart five watches (so far) I've never found two springs at the same time. I've found one spring once, one spring and a metal contact piece once, and three times I've just found empty holes. Did other people take them apart first and lose a spring? Did I lose a spring taking them apart? Either is possible, but the last time I was extremely careful because I knew there was a spring in there, and only found the one spring and a contact designed to touch the outer bezel.

The fact that the spring in the 8900 is that short just adds to the puzzle. :think:
 
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