Re: Fluke display faults OT.

[jcmassey@netspace.net.au]

At 08:07 AM 31/08/01 -0400, you wrote:
>
>Your correct, the Fluke has a flexible rubber piece with conductive pieces
>that run from the LCD plate glass
>to the gold plated connection pads on the multimeter circuit board.
>I have done exactly what you described several times and it works for a
>little while,
>then goes back to its original hard to read condition.  Maybe the rubber
>strip needs replaced?
>It's also possible that it gets miss-aligned again after handling the
>meter.
>
>Thanks,
>Rod


1) Restoring the contact (display segments fading or individual segments
'dropping out'). The rubber strip has carbon impregnated tracks. If there
is sufficient compression available, you can use 1200 (very fine) emery to
rub away a little of the rubber. Then WIPE the rubber (if you "clean" the
rubber, you will be removing carbon). Thoroughly clean the PCB gold
contacts, and wipe the conductive glass of the display. If there is
insufficient compression, replace the rubber bit. Do NOT 'build up' the
gold plated pads on the PCB with solder to increase compression, over time
the solder will pnly 'creep' until you have shorts between tracks and also
poor contacts. I think in newer meters something other than carbon is being
used, but the principle works fine.

2) Mis-alignment (wrong segments lighting up). This is exceptionally
difficult to do with fluke meters. The mechanical design makes it almost
impossible to misalign in all models I've had apart. In other
manufacturers' it is somewhat variable. 

3) Display failure. Us poor folks having to make do with 'old faithful'
that's around 20 years old start to see this (unless a meter has been left
in the sun a lot). Display failure manifests in two ways - unrecoverable
fade, and all segments being visible all the time (with varying intensity
for on/off).

4) An additional thing with some fluke meters. The 77 series one if I
recall models correctly was particulaly prone to this - the two SMD chips
on the back of the board were not necessarily hard down to the board when
soldered in place. Over time the solder cracks and the meter goes
intermittent ot just stops. Get an SMD rework tip (or a good, fine point
iron) and some good eyesight and resolder each pin, without bridging
between pins.

James Massey
Technical Manager
Industrial Technik P/L