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John Robertson John Robertson is offline
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Default Old DMM display problem

On 2019/05/23 2:45 p.m., Eremita Analogico wrote:
Hi to all,
I have collected an old (80s) HT 1100A multimeter that seem a clone of a
Fluke of that era.
It mount a classic 7106 A/D converter that drive driectly a LCD display.
When turned off, the display appear in good conditions, no black marks,
brownings or burning signs.
When I turn on the DMM, the display show almost all segments, except
when the display is not 00.0 (that appear like 88.8)
If I measure something that implies display to show fewer segments
(like, i.e., 11.1) the reading is ok without ghost segments.
If I reduce supply from 9V to around 4-5V, the display start to show
00.0 correctly, but with still some light ghost segments.
Replacing the 7106 with another don't eliminate the problem.
Do you think that I can try to solve?

How is the display connected to the PCB below it? Is it a wide flat
flexible cable or a pair of edge conductive strips? If strips is the
display firmly seated on them? If you gently press on these edges when
displaying the incorrect values do the display then show correct values?
If so, rather than taking it apart, can you insert some small bits of
foam rubber to gently press the display down when it is installed back
in the case?

John :-#)#

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