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Old 17th Sep 2021, 4:45 pm   #1
6SN7WGTB
Pentode
 
Join Date: Apr 2021
Location: Redhill, West Sussex, UK.
Posts: 106
Default Fluke 87 display fix

I have had a very trusty Fluke 87 since 1990.

After about 10 years, the display started 'losing' segments - they were actually on but hard to see anymore.

I took it apart and found how the LCD display is 'connected' to the PCB by means of what must be some sort of conductive flexible strip - but simply held against the copper tracks of the PCB.

Initially, cleaning it and the PCB and reassembling solved the problem.

However, after 6-9 months it started playing up again.

Trying all manner of contact cleaners, conductive oils and so on did not work any better - the solution now seemed to last less and less time.

Meanwhile, removing the thing had not broken off one of the fairly brittle clips - meaning that it was held even less securely to the PCb.

The solution I found that as worked now for TEN years is as follows:
1. Having removed the LCD, clean the flexible conductive pad with a mild solvent (alcohol e.g.)
2. Ditto the board
3. Apply a VERY VERY thin film of silver loaded heat sink compound to the edges of the flexible 'conductive' strip. The right result is that you have wiped it gently with a vey clean cloth and there remains a visible silver film (well - looks more grey).
4. Reassemble.

It all sounds counter-intuitive applying something conductive to a strip which must have many small adjacent contacts, but it doesn't seem to 'short' them out
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