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LCD display segment - Citizen 9100

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JAA

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LCD display segment - Citizen 9100

Post13 Sep 2013, 17:55

I'd like to get some help in diagnosing an issue with my Citizen with a 9100 module.

On the LCD display for seconds: first digit's right-lower-vertical segment is not displaying on: "0", "1", "7"
2013-09-13 08.28.02.jpg


it incorrectly shows up for "2".
2013-09-13 08.26.54.jpg


Other numbers are displaying correctly (3, 4, 5, 6, 8, 9).
2013-09-13 08.26.11.jpg


Same digit segment display the above symptoms when displaying day of the week (the exact same segment incorrectly show up in "FR") in calendar mode.


There are no other issues with the rest of the watch.

The Citizen technical manual doesn't describe this condition. I've removed the LC display panel to check the contacts and reinstalled it. I did reset by re-installing the battery (there's no separate reset procedure in the manual).

Inputs please.
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767Geoff

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Re: LCD display segment - Citizen 9100

Post13 Sep 2013, 22:30

Sounds like the display driver. Not seeing the movement the display driver may be a separate chip or built into the main IC. also not knowing the history or age of the watch there may have been damage from out gassing in the old batteries.

It does not appear to be a connection problem at the LCD panel. Check all the traces from the IC/display driver for corrosion which may be confusing the signal as the display driver interprets the digits and send that info to the display.

Cheers, geoff
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JAA

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Re: LCD display segment - Citizen 9100

Post14 Sep 2013, 00:51

Thanks Geoff. BTW, this is my first time inside a digital watch. I just took it apart again. Everything is clean, no sign of corrosion. Removed traces of dirt. Problem still persists. I'll get back to it again as I learn more about this watch.

:= :Prost:
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767Geoff

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Re: LCD display segment - Citizen 9100

Post14 Sep 2013, 02:10

Hello JAA,

I am by no means an expert, but not all bad batteries leak fluid. Some out gas which do not leave obvious evidence and this gas can seep into the IC and corrode the thin traces found in the IC plastic sandwich.

I am writing a book on HP handheld computer/calculator restorations from the early seventies to 2000. I have seen and repaired over 100 of these units and have seen the result of out gassing damage as opposed to acid leakage.

The fact that the segments appear on some digits but not others utilizing the same segment would appear (99%) to be a display logic problem and not a display problem.

Good luck! Have you tied heating the module and testing while warm and conversely, cooling the module (fridge not freezer or spray coolant) and testing. I have done the coolling and the calc worked until it warmed. I isolated, by cooling the chips individually with a spray coolant ( electronics store) the main display driver as the culprit in some cases and replaced it and voila!

Cheers, Geoff

Of course, an oscilloscope would help but that takes training ;-)
Last edited by 767Geoff on 17 Sep 2013, 03:54, edited 1 time in total.
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JAA

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Re: LCD display segment - Citizen 9100

Post14 Sep 2013, 07:33

Aha. I couldn't figure out how logic would just "go bad" on its own. Your description of outgassing in very interesting.

Heat-cold testing sounds interesting. I'm not sure what I'll do if this test works with this watch. Since I paid less than $5 for it and it works otherwise, I leave it as is for now. I think I acquire another to experiment with.

I love these old HP calculators...

Oscilloscope. I haven't touched one since the Los Angeles Olympics.
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cobra007

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Re: LCD display segment - Citizen 9100

Post14 Sep 2013, 12:28

I think it could still be the LCD itself or a connection to it. If you analyse your digits properly, you will notice that whenever the center segment is on, the right-bottom segment is also on and whenever the center segment is off, the right bottom segment is also off. That's why it does not display the numbers 0, 1, 2 and 7 correctly. My guess would be the LCD, say 60% chance.

Michel
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JAA

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Re: LCD display segment - Citizen 9100

Post14 Sep 2013, 18:53

Your analysis is correct. These two segments do go on together. The diagram shows the contacts for these 2 are adjacent. I went back in to re-clean these contacts. No success. It may be within the display itself where I couldn't access.

Thanks for your help.
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charger105

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Re: LCD display segment - Citizen 9100

Post15 Sep 2013, 03:29

The zebra strips are a likely culprit.
Try cleaning these too.
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Re: LCD display segment - Citizen 9100

Post15 Sep 2013, 15:06

charger105 wrote:The zebra strips are a likely culprit.
Try cleaning these too.


Charger105 could well be right on this one.
What i did myself is sanding the zebra strips on the side where the "indents" are (i don't know what else to call them) so the strip is all flat again, it is tricky but it can be done.
I repaired a few watches with segment problems this way.
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JAA

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Re: LCD display segment - Citizen 9100

Post16 Sep 2013, 05:04

Thanks for the input. Based on your advice, I sanded the rubber strip with 800 grit. Under 10x loupe, they appear to be in good shape and are uniformly flat so I only applied very light pressure. I also cleaned the contacts with alcohol. The procedure improved another previously dim segment somewhat; but the original problem persists.
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cobra007

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Re: LCD display segment - Citizen 9100

Post16 Sep 2013, 08:30

JAA wrote:Thanks for the input. Based on your advice, I sanded the rubber strip with 800 grit. Under 10x loupe, they appear to be in good shape and are uniformly flat so I only applied very light pressure. I also cleaned the contacts with alcohol. The procedure improved another previously dim segment somewhat; but the original problem persists.


You could take a 1.5V battery and apply a voltage directly to the LCD segments (just follow their traces, they're a bit hard to see but not impossible). Once you found the 2 segments in question, see if you can control them individually or if perhaps the right-bottom segment always follows the state of the center segment.

Michel
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Re: LCD display segment - Citizen 9100

Post16 Sep 2013, 15:23

cobra007 wrote:
JAA wrote:Thanks for the input. Based on your advice, I sanded the rubber strip with 800 grit. Under 10x loupe, they appear to be in good shape and are uniformly flat so I only applied very light pressure. I also cleaned the contacts with alcohol. The procedure improved another previously dim segment somewhat; but the original problem persists.


You could take a 1.5V battery and apply a voltage directly to the LCD segments (just follow their traces, they're a bit hard to see but not impossible). Once you found the 2 segments in question, see if you can control them individually or if perhaps the right-bottom segment always follows the state of the center segment.

Michel



Please be advised, that applying a steady DC voltage to an LCD display for a period of time can damage the display by polarizing the liquid crystals in one direction. Short time application is OK, just don't linger when using this method to check the various segments.

Ole Joe
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cobra007

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Re: LCD display segment - Citizen 9100

Post17 Sep 2013, 00:30

Ole Joe wrote:
cobra007 wrote:
JAA wrote:Thanks for the input. Based on your advice, I sanded the rubber strip with 800 grit. Under 10x loupe, they appear to be in good shape and are uniformly flat so I only applied very light pressure. I also cleaned the contacts with alcohol. The procedure improved another previously dim segment somewhat; but the original problem persists.


You could take a 1.5V battery and apply a voltage directly to the LCD segments (just follow their traces, they're a bit hard to see but not impossible). Once you found the 2 segments in question, see if you can control them individually or if perhaps the right-bottom segment always follows the state of the center segment.

Michel



Please be advised, that applying a steady DC voltage to an LCD display for a period of time can damage the display by polarizing the liquid crystals in one direction. Short time application is OK, just don't linger when using this method to check the various segments.

Ole Joe


Yes, that is true but I think that counts more for days or weeks rather than seconds or minutes.

Anyway, just to be on the safe side, only apply the voltage for a few seconds maximum.

Michel

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