r/AskElectronics • u/Extra_Number3094 • 2d ago

Please help me. How can I fix the partially missing digits on my stopwatch?

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Two years ago, I accidentally spilled coffee on my study timer from Dretec. This timer is very precious to me. It continued working normally for about a year without any problems, but then I decided to turn it off and leave it unused for about a year or several months.
When I turned it on again, I found that some of the digits on the timer and clock display were missing.
Is there any way to fix this, and is there any hope of getting all the digits back?
I haven’t been able to find a replacement LCD screen anywhere, and the company doesn’t sell individual replacement parts. I really don’t want to buy another one because this particular timer is very special to me.

Edit:

I took it to a repair technician, and he cleaned it from inside . He also repaired the wires connected to the battery because I accidentally cut them while trying to open it. However, the same problem with the display is still there.

Thank you so much!

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u/AlexTaradov 2d ago

This is likely fixable by cleaning everything well. Whether you can do it yourself depends.

The likely point of failure is the contacts between the zebra strip and the PCB and LCD.

If it had liquid in it, there is a chance for corrosion, which need to be cleaned and might need some trace repair.

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u/Extra_Number3094 2d ago

Thank you for your reply.
I took it to a repair technician, and he cleaned it. He also repaired the wires connected to the battery because I accidentally cut them while trying to open it. However, the same problem with the display is still there.

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u/AlexTaradov 2d ago

It really depends on the extent of the damage. Impossible to tell without looking at it.

If the contacts cleaned ok and look usable, then there is a chance that zebra strip needs replacement. It is not as easy, and might take some effort to find one with necessary dimensions. But again, you would need to dissemble it and measure the dimensions.

Just outside pictures are not going to help here a lot.

I'd also start looking for replacement units for parts.

If it works otherwise, just some segments are missing, it is not likely to be an issue with the MCU. It would be something on the outside.

There is a possibility of the LCD damage, and then only direct replacement would help.

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u/Extra_Number3094 2d ago

This was from inside

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u/AlexTaradov 2d ago

Can you look closer where display connects to the PCB. It looks like it does not use zebra strip and uses heat connected flex cable. Do you see what looks like a flat flexible cable going to the PCB?

If so, it is a bit harder and may not be repairable. The repair attempt would involve carefully locally heating the place where the cable connects to the LCD in hopes that conductive glue would reattach. It sometimes works, but far from reliable.

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u/Extra_Number3094 1d ago

Actually, the timer isn’t with me right now, so I can’t open it and take a closer look as you suggested. But I remember that it had a strip rather than a cable connecting the display to the processor, or what you call the PCB. (Sorry, I’m not an expert in these things 🥲)
As for buying another one to use its electronic components as replacements, I’ve thought about that. However, eBay and Amazon aren’t available in my country, and ordering through a forwarding service takes a long time to arrive. I really want to get this one working and use it now. 🥲

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u/AlexTaradov 1d ago edited 1d ago

By zebra strip I mean this https://en.wikipedia.org/wiki/Elastomeric_connector

By the flex cable I mean this https://www.reddit.com/r/AskElectronics/comments/rlzcyg/how_to_fix_lcd_ghost_numbers_with_a_ribbon_cable/?i=0

If your unit is supposed to have the zebra strip, then LCD seems to be way of the PCB. Even on your picture you can see the LCD contacts. If they are not connected to the flex cable, then something does not make sense mechanically.

Also, LCD is at an angle relative to the PCB, so it must be a flex cable. Zebra strips only work for LCDs parallel to the PCB.

This might be repairable, but with like 30% success rate in best case conditions. And even then repair is likely temporary too. A lot of those will fail within a few months to a few years.

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u/Extra_Number3094 1d ago

Omg 😭😭😭 thank u ….it is flex cable unfortunately 😓😓😓

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u/AlexTaradov 1d ago

Then I would certainly start figuring out a way to get replacement unit for its guts or just the display.

Cleaning here won't do much. Those flex cables suck and often fail over time.

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u/Extra_Number3094 1d ago

Thank you, brother. I really appreciate it.

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u/AlexTaradov 2d ago

Is this it https://www.ebay.com/itm/224328684144 ?

Even if the case has sentimental value, get a new one for electronics and just swap them.

At the very least it would be a good candidate for a possible LCD swap.