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How to completely fix Seiko G757 faded/broken LCD.

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supercow9001

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How to completely fix Seiko G757 faded/broken LCD.

Post22 Mar 2017, 21:18

As many G757 owners have discovered, the Seiko G757 tends to lose contrast in the screen over the years until the screen becomes unreadable. You can find many G757s on ebay that have this problem, and they're typically much cheaper than a completely working one. I've seen many different suggestions for how to fix this problem, ranging from disassembling the watch and leaving the PCB in your oven for a half hour, to dropping it in a bath of various cleaning chemicals. After several unsuccessful attempts to restore my G757s, I have finally found a way that addresses the root problem with the G757.

I noticed that on all of mine, the contrast got progressively worse every fifteen seconds, whenever another quarter of the second display was filled. This problem wasn't present when the watch was left in dual time mode, or another mode where the second display wasn't filling completely.

On the G757's PCB, there is a row of four rectangular SMD capacitors labeled "Upconverter Condenser" on the G757 service manual/parts list. These wear out after a few decades and must be replaced.

Normally, these capacitors should be 170 or 180 nanofarads, but some of mine were as low as 130.

To repair the watch, you'll need four 180 nanofarad capacitors.


What you need:
Soldering Iron
Helping Hands (Stand with magnifying glass and alligator clips for holding what you solder)
Tweezers
4x 180 nanofarad SMD ceramic capacitors. Metric 2012 size are slightly smaller than the original, but they should fit.
Thin screwdriver or solder scraper for unscrewing the PCB from the case
Magnet for holding screws THIS IS IMPORTANT

Optional:
Solder wick. These capacitors are small enough that laying a wedge tipped soldering iron over the top was enough to desolder both ends, but a solder wick would have probably made it easier.


Repairing the watch is pretty simple. Start by opening the outer case and taking out the PCB + inner case assembly. There's a metal clip with four edges holding on the screen, the mirror, and the plastic spacer. This can be removed by prying open the four clips attached to the green case.

The LCD interfaces with the PCB through two rubber strips that are commonly referred to as "Zebra stripes." These can safely be detached from the screen and interchanged with each other. The zebra stripes do have an up side and a down side. If you take a close look at them, you should see one side that appears to have a few thicker lines between the normal lines. This is the side that should be touching the PCB when the watch is reassembled.

With the case and LCD removed, carefully unscrew the PCB from the green case. If there's any corrosion or battery residue on it, the PCB can be cleaned with rubbing alcohol and a Q-tip, or in a rubbing alcohol bath.

With the capacitor side up, place the PCB in your helping hands.

Desolder the four capacitors and replace them with the new ones. If you don't have a soldering wick, you can lay the flat side of a tinned wedge tipped soldering iron over the top of the capacitors.

Now, you can reassemble the watch and it should have its contrast completely restored. This should work for all models of the G757.
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Adam

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Re: How to completely fix Seiko G757 faded/broken LCD.

Post23 Mar 2017, 00:50

Sounds like fun. I have enough broken/flashing/missing digit G757s here to play around with. Where do I find the 180 nanofarad SMD ceramic capacitors. Metric 2012?


regards

Adam
http://www.digital-watch.com - online database of 2000+ watches, manuals and adverts from the 70s-90s
http://www.vintagelcd.com - Vintage Digital Watches for sale
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supercow9001

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Re: How to completely fix Seiko G757 faded/broken LCD.

Post23 Mar 2017, 00:55

You should be able to find them on digikey.
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nick0123

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Re: How to completely fix Seiko G757 faded/broken LCD.

Post24 Mar 2017, 02:07

@supercow9001 — would this be the Digikey product?

http://www.digikey.com/scripts/DkSearch ... 6979901528
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supercow9001

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Re: How to completely fix Seiko G757 faded/broken LCD.

Post24 Mar 2017, 02:17


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