Repaired Digital Multimeter Display Screen Turning To A Dark Patch
I am having an old digital Multimeter which has not been used since last 18 years. Because it was little bulky to carry on field work and consuming more place in tool bag. In this covid lock down period I have started some maintenance work of my old tools which I am rarely used.
So when I have taken this multimeter on my workbench I found the display screen is having some dark black patch on it in and numbers are difficult to read.
On opening I found 9v Battery was leaked and dried in side. I have cleaned the meter from inside and turned it on by putting new 9V battery. On testing I found all the ranges working fine but reading on screen is blurry and unable to read number clearly.
So I have decided try to repair this problem. I have removed the LCD display unit. It looks like liquid spilled inside the screen.
Here I have no idea what size and type of screen I have to get replaced with and if I get the screen may work may not work and it is not economical also. So I have only two options either tries to repair and if no success then salvage the parts.
This type of screen is made of different layers i.e. From top to base:
1) Plastic Protective Layer
2) Polarizing filter sticker
3) Glass assembly and liquid crystal ink sandwich
4) Reflective foil sticker
Note: Edge & Corner of this glass display is very sharp so take care while handling.
Now from top layer removed Polarizing filter film (Dark Black) using sharp blade.
(Be careful while removing because this film is firmly stuck on the screen by glue, in hurry…. while removing the film one side corner is torn down by me) that also I have cleaned with thinner and IPA with use of cotton cloth ……
Then I have removed LCD Display and removed the Reflective Silver like foil sticker (Shown on above pic) from the base of LCD & Wiped out the sticker glue from the Glass of LCD using thinner and IPA with use of cotton cloth.
The bottom reflective film layer has simply lost some of its shiny paint (shaped like a dark oval), due to age and temperature, hence unable to reflect light properly and showing patch on the screen.
Now once you remove the bottom reflective film you cannot reuse it because it will not remain in the shape as earlier. for solution to this I have removed one backlight reflective sheet from old damaged LCD screen of the laptop and cut it down in exact shape.
Now it is time to re assemble the unit ….
Now it is time to see result
As damaged corner is not disturbing the digits it is ok for workbench use. This way I saved my multimeter going to scrap.
This article was prepared for you by Yogesh Panchal who works as a Computer Hardware Engineer in Mumbai India.
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Note: You can check his previous repair articles in the link below:
https://www.electronicsrepairfaq.com/doorbell-repaired
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babu ms
August 12, 2020 at 9:47 pm
Very good job. I have learned about display board construction,Thanking you and expect many more news letter.
Yogesh Panchal
August 14, 2020 at 12:39 am
Babu Ms,
Thanks! for your Comment....
Gilberto
August 12, 2020 at 10:04 pm
Nunca hubiera intentado reparar de esa manera una pantalla como esa. No cabe duda que es usted una persona inteligente, capaz y perseverante.
Felicidades desde México!!
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I would never have tried to repair a screen like that in that way. There is no doubt that you are an intelligent, capable and persevering person.
Congratulations from Mexico !!
Yogesh Panchal
August 14, 2020 at 12:42 am
Gilberto,
Many thanks! for encouraging your words.
Parasuraman S
August 12, 2020 at 10:24 pm
Vow! I never ventured to repair this type display and I am happy to learn how it works and what we can do to restore! Very useful article! Many thanks for sharing!
Yogesh Panchal
August 14, 2020 at 12:44 am
Sir,
Thanks! for for your kind comment....
Tayo
August 12, 2020 at 10:29 pm
Excellent knowledge transfer. I will be sure to save a few LCD screens on broken units in case I ever need to do this repair.
Question: Could you have not used the polarizing film from the donor LCD screen to replace the one you accidentally damaged?
Yogesh Panchal
August 14, 2020 at 12:57 am
Tayo,
Thanks! for your comment...
I have used Backlit Reflector sheet from donor LCD that is Laptop's Color LCD and also tried polarized film but it would not worked maybe polarize film type is different.
B.R.Kini
August 12, 2020 at 10:29 pm
Very informative and very well presented .I was looking for a repair article like this for long time.
Thank you once again for bringing up a topic like this in this website .
Thandosebe Mavimbela
August 13, 2020 at 4:25 am
I was know nothing but because this website I have gained knowledge
Yogesh Panchal
August 14, 2020 at 1:01 am
Your welcome! sir,
Thanks! to Jestin sir for providing this wonderful platform to share ideas and experience.
Yogesh Panchal
August 14, 2020 at 12:59 am
B.R.kini,
Your welcome! sir.
Waleed Rishmawi
August 12, 2020 at 11:21 pm
A new experience for me. Thanks for sharing
Yogesh Panchal
August 14, 2020 at 1:03 am
Your Welcome! Waleed.......Welding machine Expert!!
Raj
August 12, 2020 at 11:57 pm
Interesting to learn that lcd display could be repaired at micro level..Great..thanks for sharing
Yogesh Panchal
August 14, 2020 at 1:07 am
your Welcome! Raj.....
for This type of repair there is 70% Chances to get positive result because some LCD is sealed in Glass itself that can not be opened.
Albert van Bemmelen
August 13, 2020 at 1:50 am
Nicely done Yogesh! Using part of the reflective sheet of an old defect laptop is an interesting fact to know. Always a good reason to save spare parts for new repair situations.
Yogesh Panchal
August 14, 2020 at 1:19 am
Thanks! Albert,
You are absolute right salvaging parts form the irreparable equipment
may be because lack of new parts availability recently i have got one laptop for repair and i found motherboard PCB itself Internal short.....
Yes PCB..... these are multi layer PCBs and internal layer showing short and this type of problem is irreparable and for this type of equipment you can give buyback offer to customer also.
Imoudu ONWUMAH
August 13, 2020 at 2:08 am
Wow! Excellent repair,I have learned a new thing. I have two dmm on my work bench that need repairs
Yogesh Panchal
August 14, 2020 at 1:20 am
Imoudu ONWUMAH,
Thanks! for your comment.
Vitalice Were
August 13, 2020 at 2:53 am
Thank you Mr Yogesh for sharing and enlightening me on what to do .Great work.
Yogesh Panchal
August 14, 2020 at 1:21 am
Your Welcome! Vitalice Were,
Gary Cale
August 13, 2020 at 11:12 am
Absoloutely amazing!
Yogesh Panchal
August 14, 2020 at 1:22 am
Thanks! Gary Cale.
cipriano olivar
August 14, 2020 at 7:12 pm
interesante y necesaria la información,me gusto muchas gracias
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interesting and necessary information, I liked it thank you very much
Yogesh Panchal
August 15, 2020 at 9:47 pm
Your welcome!
Joven Urbano
August 17, 2020 at 12:37 am
I have the same problem with my DMM which I haven't used since 2003. I was planning to replace the display so I can still use it. You gave me an idea on what do do with it. Thanks a lot for sharing!
Yogesh Panchal
August 20, 2020 at 3:47 pm
Your Welcome! Joven
Humberto
August 19, 2020 at 12:00 pm
Wow! I had not seen this kind of repair before. Congrats.
Yogesh Panchal
August 20, 2020 at 3:47 pm
Thanks! Humberto
vinay
September 16, 2020 at 4:28 am
Hi folks,
Where can we buy the reflective sticker foil in India?
I am searching for almost 2 weeks with no clue and the local electronic market I could not find it.
Please advice.
Regards,
Vinay
S. P. Sharma
January 26, 2022 at 7:59 pm
Thanks for the info. Can v use adhesive aluminium tapes available online to replace silver of LCD of digital meters?
If someone attempted pl share.