Longines G - II Dual Display Crystal

[bucko170]

I recently purchased a Longines G - II dual LCD LED display, the bottom crystal is chipped, ideally i would like to have this replaced. I found a place selling\fixing crystals on the net but it means sending the watch to the USA which i don't really want to do, does anyone know of any alternatives closer to home, i would prefer a replace and fix service as i'm cack at repairs. Mick

[azimuth_pl]

a good alternative is plexiglass and you won't even tell the difference.
you can do it on your own easily.
a pack of tic-tac's is a good source

[CompuChron]

Hi,
I have a Longines gemini II which needs both crystals redone.
Waht do you use tu cut the plexi properly.
How do you make a model?
Thanks

[azimuth_pl]

Plexi is transparent so you can place it on top of the case and draw a line with a permanent marker. Also making a model in cardboard first is good so you can draw the contour on the plexi using the cardboard model.
I use a razor blade or scalpel to cut the contour and gently brake the plexi.
afterwards I file down the sharp edges until it fits properly in the case.

[CompuChron]

Thanks,
I need a box of tic tac now ,still wondering about the flavour...

[azimuth_pl]

the new lemon-mint flavor is good* :)
for beginners I suggest to cut the contour a bit bigger than the final dimension and file down more plexi. use displex or alike for that final touch.

(*subject to availability on certain markets)

[CompuChron]

lemon is good but the box is yellow here...

[CompuChron]

Finally I choose "Mint" , i thought it would be the best.

Unfortunately, I worked like a pig.

I cut nice pieces of plexy that fit perfectly.
And then I glued them back in place with some extra strong super glue:bad idea!
I have awfull traces of glue underneath my crystal....arghhhhhh
What should I have used to glue the plexy?

I received the watch this morning , bought on ebay as tested and non working. After a light cleaning , it appears to work but not as it should:
Either both display stay on , or only the running second of the LCD.
I suspect a short cut somewhere? Any clue?
Wil it work like that with the led button always pushed?

[azimuth_pl]

ha, ha
never use super glue on acrylic transparent plastic.
use A+B strong epoxy or rubber-like glue for fitting crystals on watches.

your Gemini must have a short on the buttons or battery contact or maybe one of the tiny wires on the IC is shortcircuiting. as a last resort you will need to open the cover on the board and check with a loupe.

[Higgie]

The problem with your button is probably that it's too sensitive.
Normally when the button is not pushed it should have 0 volts over it, but the transistor inside your module sees a higher voltage resulting in showing the date.
The solution is very simple, solder a resistor from the button to "ground".
In my case a 4.7 Kohm resistor did the trick.
This is also applicable to other modules with the "button always pushed" fault.



This Pulsar had the same problem, a 47Kohm resistor did the trick here.



Opening a led/lcd module:
Carefully take the module out of the case, note it has a sort of spring on the side ( at 4 o clock see my pic.) to preveny it from rotating in the case and to make proper contact with the case.

Remove the three clips that keep the upper and lower half together by pushing them outwards on the display-side.
Now very carefully pull the clear red side from the bottom side. Note the two clear "pins on the side, be careful not to break them.

Watch out for the bondings on the led display, these are exposed now. Touching them will kill the led display.

[CompuChron]

thanks for the advices .
Concerning the module, i took the easy way , I had a NOS module waiting for its case in a drawer for years , so i put it in the case.
If anyone is interested in my "almost working" module, I could trade it.
Note I didn't try to repair it in anyway.
And I compared with my nos module , it acts just like 1 button is always pressed.
Concerning the crystal , it will stay like this until further notice, I'm afraid to break the red part under the crystal when I take it off.
What's the best way to get rid of the super glue?
Heat?

[azimuth_pl]

Higgie,
where do you buy resistors? and without much electronics equipment how do you check what kind of resistor you need?

CompuChron,
super glue is based on cyonide and very often damages the plexi permanently. it might be quicker to make a new crystal from tic-tacs.
super glue from metal parts should come off quite easily by scraping the surface gently.

[Higgie]

Higgie,
where do you buy resistors? and without much electronics equipment how do you check what kind of resistor you need?

Pjotr, Ebay where else? Search for SMD resistors, the 0805 series is the smallest. http://cgi.ebay.nl/SMD-0805-50-Value-Resistors-32-Value-Capacitor-Kit_W0QQitemZ230217602858QQihZ013QQcategoryZ36335QQrdZ1QQssPageNameZWD2VQQcmdZViewItem?_trksid=p1638.m122

And for the value? Its just trial and error, start low at about 1K and go up till you get the value that's not working any more, then go two steps lower.
Why use a high value? The higher the value, the less drain on the batteries.

[retroleds]

CompuChron,
super glue is based on cyonide and very often damages the plexi permanently. it might be quicker to make a new crystal from tic-tacs.
super glue from metal parts should come off quite easily by scraping the surface gently.

Super glue is removed with acetone...fingernail polish used to have acetone, now most don't.

The tic-tac box isn't terrible, but it is styrene plastic - cracks easily compared to acrylic. I have stuff to mail you Olivier.....I can throw in some NOS clear acrylic screens and a few nice flat red one's also. As the others said - use epoxy, 5 minute low strength is sufficient.....cleans up nicely with alcohol while wet. With the glass out you can place the watch face down on a scanner, scan it - a nice line will be where the inset for the lens is(you can bring this out by adjusting the contrast of the scan). Print to label material and you have a nice template to get you very close. The red material can be scanned by itself....somewhere I already did this.

In liu of label material, spray adhesive/fixative works very good and doesn't harm most plastic. This is how most people cut glass for "Stained glass" projects....one of my other hobbies.

[CompuChron]

Thanks guys!
When I'm talking of the red part, I'm talking about the small thin red screen under the upper crystal where "LONGINES" is printed and I don't want to damage that.
So,I'll try when my tic tac timescreen is damaged , I don't want to make it worth than it is.
(pictures coming!")