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Old 18th Sep 2021, 3:27 pm   #3
Leon Crampin
Octode
 
Join Date: Nov 2005
Location: Surrey, UK.
Posts: 1,624
Default Re: Fluke 87 display fix

Relevant to the post, but differing in application, I have a 30 year-old Drayton programmer controlling my boiler. It is fitted with an LCD display slightly larger than that used by Fluke, and developed the "missing segments" problem.

Dismantling, cleaning the tracks with a rubber (Drayton just left them solder coated...) and finishing off with IPA on a cotton bud resulted in a fix - but only a temporary one. After a couple of sessions, the segments still eventually faded.

The real fix was to file down the edge of the display holder by about 0.5 mm and add a corresponding shim to the other side of the pc board to maintain a tight fit. This has the effect of increasing the preload on the "zebra" strip connecting the pc to the display panel.

As with most elastomers, especially when heat cycled near a boiler, the strip had clearly relaxed and consequently there was inadequate contact pressure to give a reliable connection to all conductors.

Increasing the strip preload effected a lasting fix. I "rewarded" the controller by fitting a new set of electrolytics at the same time.

Roll on next Winter - if I can afford the gas.

Leon.
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