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Other Vintage Household Electrical or Electromechanical Items For discussions about other vintage (over 25 years old) electrical and electromechanical household items. See the sticky thread for details. |
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6th Feb 2017, 1:44 pm | #1 |
Pentode
Join Date: Feb 2015
Location: Conwy, Clwyd, UK.
Posts: 246
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Digital scales LCD problem
Hi folks,
once again my bench is clogged with dull broken consumer electronics that I don't know where to start on! This time it is a commercial scales made by UWE. It must be 20 years old or more but weighs and counts perfectly - except the LCD display is showing broken characters or displaying wrong segments. It is still possible to decipher what the digits are meant to be, most of the time.... I think this is beyond my capability, particularly without a service manual or circuit diagram. But I just thought I would ask - are there any typical causes for this kind of problem? I presume there will be a LCD driver IC but most of the chips have white labels stuck on them so I can't tell what they are yet! Thanks Glyn |
6th Feb 2017, 2:11 pm | #2 |
Banned
Join Date: Dec 2013
Location: Middlewich, Cheshire, UK. & Winter in the Philippines.
Posts: 3,897
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Re: Digital scales LCD problem
It's classic failure mode for LCD's especially the glass encapsulated ones.
You may find a replacement on a Hong Kong or Chinese auction site that sells surplus electronics. There should be a number on the display itself, Google can be your friend. The driver chips normally are either OK or totally blown. |
6th Feb 2017, 2:56 pm | #3 |
Octode
Join Date: Jan 2014
Location: Oban, Scotland, UK.
Posts: 1,129
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Re: Digital scales LCD problem
You could check to see if the LCD connections are made via 'zebra strip' which is often a troublesome cause of misreading LCDs.
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6th Feb 2017, 3:43 pm | #4 |
Dekatron
Join Date: Feb 2003
Location: Cottingham, East Yorkshire, UK.
Posts: 5,761
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Re: Digital scales LCD problem
If it does indeed have 'zebra strip' connections but cleaning the strip and the LCD edges with I.P.A doesn't do the trick, it's worth checking if there are any electrolytic capacitors, and if so, they might have developed a high ESR, so it could be worthwhile changing them. Just supposition on my part - much depends on whether it was put together in a way that it can be taken apart.
Good luck with it.
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David. BVWS Member. G-QRP Club member 1339. |
6th Feb 2017, 7:21 pm | #5 |
Pentode
Join Date: Feb 2015
Location: Conwy, Clwyd, UK.
Posts: 246
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Re: Digital scales LCD problem
The display has pins in a socket like a big IC - definately thru-hole technology which probably points to it being older than my estimate. I hadn't considered the display itself being the problem. There are numerous electrolytics on the board, if i can identify what drives the display i may test a few before going further. I don't know how costly these scales might be, but it could be bullet-biting time for this set. Looks like they've lived a full life!
Cheers Glyn |
6th Feb 2017, 9:04 pm | #6 |
Dekatron
Join Date: Jun 2009
Location: Staffordshire Moorlands, UK.
Posts: 5,270
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Re: Digital scales LCD problem
these are usually custom lcd glass due to the numerous annunciators, kg,lb,zero,tare etc.
I've got a UWE platform scale here, but a modern one. Nice thing for a chinese budget unit.
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Kevin |
6th Feb 2017, 9:37 pm | #7 |
Octode
Join Date: Oct 2003
Location: Newbury, Berkshire, UK.
Posts: 1,770
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Re: Digital scales LCD problem
Yes, I invested in one a few years ago (Jennings Jship series). Not a lot of money and calibrated well against a known good set. Also has the advantage that it speaks the weight, which mean if the display ever goes TU the unit is still useful.
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Chris |