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'[EE]: Fluke meter LCD problem. Crossed threads'
2002\08\11@025021 by Robert Rolf

picon face
The simple way to fix the 'cross threaded' screw problem is to turn them
backwards until they click, then forward. The 'click' is the screw thread
falling off the edge of the thread in the plastic, so that they are
now aligned, and so you no longer cut new threads. This 'trick' has
allowed me to reuse screws in plastic cases for decades without the hole
becoming worn or loose.

The conductive part of Z-stipes is usually carbon in rubber. Several hundreds
of ohms resistance, which is nothing since the display draws nearly no current

Robert

Randy Jones wrote:
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> {Original Message removed}

2002\08\12@053447 by Alan B. Pearce

face picon face
>The conductive part of Z-stipes is usually carbon in
>rubber. Several hundreds of ohms resistance, which is
>nothing since the display draws nearly no current

I used to service a series of computers made by Harris, which had daughter
boards mounted on a mother board, and connected by these things. Gave us no
end of trouble, until they changed to another type of insert which had thin
gold coated metal strips wrapped around the silicon rubber strip. The carbon
conductive strips seem to be extremely finicky despite the incessant
cleaning and careful use of the torque driver to the correct setting.

The carbon filled ones had obviously been a problem for many years before
they changed.

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2002\08\12@111142 by M. Adam Davis

flavicon
face
The only thing the extra resistance does is slow down the display
response time (why you'll never see zebra in any LCD but the simplest).
The display is, electrically, a leaky capacitor.  The resistance makes
it take longer to 'charge'.  Two more interesting things - the LCD
chemical breaks down over time if there is a net DC current across it,
which is why they are always driven with AC, and why multiplexing can
become quite involved.  Secondly, newer LCD drivers for high end
displays overdrive the segments for a brief instant at the start of the
waveform to enhance reaction time.  There are even variations in the
startup charge depending on what level of twist the segment had previous
to the new setting.  LCD controllers are going more torwards
proportional control - I can't wait to see if they make full PID  ;-).
Too bad it's not a real closed loop.

-Adam

Robert Rolf wrote:

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>>{Original Message removed}

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