I have a Fluke 27 where some of the segments of the display do not
darken properly. Is this a known problem, and is there some way to
fix it?

cheers, Paul - VA7NT - email:

Many such devices connect the LCD to it's controller board with a layered
elastomer (rubber, to ordinary folks) that alternates conductive and
non-conductive layers. This elastomer structure just presses against pads
on a PC board. I've verified this part by taking apart dead watches and
calculators.

What I haven't verified is the failure mechanism or what to do about it.
The story that I've heard is that the PC board gets dirty or corroded and
fails to make contact, or the elastomer looses it's stretch, or both. In
the first case you're supposed to clean the PC board (pencil erasers are
_supposed_ to work here), in the second you either get a new display or you
find a way to jam it tighter against it's PC board. This was treated in a
QST article some time back, but I can't remember the year, much less the
precise issue.

"Paul Erickson" wrote in message
...
I have a Fluke 27 where some of the segments of the display do not
darken properly. Is this a known problem, and is there some way to
fix it?

cheers, Paul - VA7NT - email:

Tim Wescott wrote:

Many such devices connect the LCD to it's controller board with a layered
elastomer (rubber, to ordinary folks) that alternates conductive and
non-conductive layers. This elastomer structure just presses against pads
on a PC board. I've verified this part by taking apart dead watches and
calculators.

AKA: Zebra strip.

What I haven't verified is the failure mechanism or what to do about it.
The story that I've heard is that the PC board gets dirty or corroded and
fails to make contact, or the elastomer looses it's stretch, or both. In
the first case you're supposed to clean the PC board (pencil erasers are
_supposed_ to work here), in the second you either get a new display or you
find a way to jam it tighter against it's PC board. This was treated in a
QST article some time back, but I can't remember the year, much less the
precise issue.

The plating on the pc board oxidizes, and the rubber hardens due to a
chemical reaction. You can usually clean the zebra strips and PC board
with 100% Isopropyl alcohol, but Fluke should have replacement strips
fairly cheap. The cal lab where I used to work would clean the boards
and strips a couple times, then replace the strips.


--
We now return you to our normally scheduled programming.

Michael A. Terrell
Central Florida

"Michael A. Terrell" writes:
Thanks very much.

cheers, Paul

Tim Wescott wrote:

Many such devices connect the LCD to it's controller board with a layered
elastomer (rubber, to ordinary folks) that alternates conductive and
non-conductive layers. This elastomer structure just presses against pads
on a PC board. I've verified this part by taking apart dead watches and
calculators.

AKA: Zebra strip.

What I haven't verified is the failure mechanism or what to do about it.
The story that I've heard is that the PC board gets dirty or corroded and
fails to make contact, or the elastomer looses it's stretch, or both. In
the first case you're supposed to clean the PC board (pencil erasers are
_supposed_ to work here), in the second you either get a new display or you
find a way to jam it tighter against it's PC board. This was treated in a
QST article some time back, but I can't remember the year, much less the
precise issue.

The plating on the pc board oxidizes, and the rubber hardens due to a
chemical reaction. You can usually clean the zebra strips and PC board
with 100% Isopropyl alcohol, but Fluke should have replacement strips
fairly cheap. The cal lab where I used to work would clean the boards
and strips a couple times, then replace the strips.


--
We now return you to our normally scheduled programming.

Michael A. Terrell
Central Florida

Are there any suppliers of "generic" zebra strip? I have a handheld that
needs this fix when I get a round tuit, and I fear that they may not have
parts for it (I'm just borrowing trouble, but you're on the line...).

"Michael A. Terrell" wrote in message
...
Tim Wescott wrote:

Many such devices connect the LCD to it's controller board with a
layered
elastomer (rubber, to ordinary folks) that alternates conductive and
non-conductive layers. This elastomer structure just presses against
pads
on a PC board. I've verified this part by taking apart dead watches and
calculators.

AKA: Zebra strip.

What I haven't verified is the failure mechanism or what to do about it.
The story that I've heard is that the PC board gets dirty or corroded
and
fails to make contact, or the elastomer looses it's stretch, or both.
In
the first case you're supposed to clean the PC board (pencil erasers are
_supposed_ to work here), in the second you either get a new display or
you
find a way to jam it tighter against it's PC board. This was treated in
a
QST article some time back, but I can't remember the year, much less the
precise issue.

The plating on the pc board oxidizes, and the rubber hardens due to a
chemical reaction. You can usually clean the zebra strips and PC board
with 100% Isopropyl alcohol, but Fluke should have replacement strips
fairly cheap. The cal lab where I used to work would clean the boards
and strips a couple times, then replace the strips.


--
We now return you to our normally scheduled programming.

Michael A. Terrell
Central Florida

"Tim Wescott" writes:
Thanks very much.

cheers, Paul

Many such devices connect the LCD to it's controller board with a layered
elastomer (rubber, to ordinary folks) that alternates conductive and
non-conductive layers. This elastomer structure just presses against pads
on a PC board. I've verified this part by taking apart dead watches and
calculators.

What I haven't verified is the failure mechanism or what to do about it.
The story that I've heard is that the PC board gets dirty or corroded and
fails to make contact, or the elastomer looses it's stretch, or both. In
the first case you're supposed to clean the PC board (pencil erasers are
_supposed_ to work here), in the second you either get a new display or you
find a way to jam it tighter against it's PC board. This was treated in a
QST article some time back, but I can't remember the year, much less the
precise issue.

"Paul Erickson" wrote in message
...
I have a Fluke 27 where some of the segments of the display do not
darken properly. Is this a known problem, and is there some way to
fix it?

cheers, Paul - VA7NT - email: