Digital scales LCD problem

[ToneArm]

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

[Boater Sam]

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.

[kellys_eye]

You could check to see if the LCD connections are made via 'zebra strip' which is often a troublesome cause of misreading LCDs.

[David G4EBT]

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.

[ToneArm]

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

[McMurdo]

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.

[evingar]

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.