EEVblog 1425 - Fluke Repair 2 Electric Boogaloo

Part 2 of the Fluke 23 multimeter repair by digging into the bunker meter archives from episode #84
Experimenting with alfoil

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#ElectronicsCreators

[conodigrom]

It looks like the air creeped under the polarizing filter, oxidizing the silver layer. In the center oval, more or less where the lcd pressure kept the two layers pressed together, keeping the air(and thus the oxigen) out.

[juskim]

Someone: "Tell me you're experienced without saying a word."
Dave: *Begins to show an entire collection of multimeters dating all the way back to the Roman ages

[WacKEDmaN]

the adhesive they use to stick the polarising layer eats into the foil with UV activation...
nice collection of meters!

[danmackintosh]

I used to mess with LCD's a lot as a kid (even tempts me now, as a grown kid!), flipping the polarising film to make a negative display on old watches and stuff like that. Just seemed super cool back then how you could make such a huge difference to the look of an old Casio knockoff just with a steady hand and no money in.

[WizardTim]

Any half decent electronics engineer should know this is the number one symptom of an LCD that is low on magic blue smoke, disappointed you ruined it instead of refilling it but at the very least it was interesting to see that your hack did kind of work, it was at least a cheap fix, magic smoke can be very expensive sometimes.

[gusmartin]

Zebra strips work great to repair the Fluke 120 series scopemeter LCS’s. Only works to fix the horizontal lines. Just remove the hot bar contacts and replace them with an appropriately sized zebra strip. I used kapton tape pulled tightly from the top LCD glass to the PCB in order to keep pressure on the the zebra strip. Alignment is tricky though. I had to message the zebra strip to one side or the other in order to get the contacts aligned due to the fine lead pitch on these displays.

[isosmxy]

As an EE/MSE person in microelectronic Fab this reminds me of making a silver mirror with silver nitrate. To demonstrate the Tollen's reagent, you can crash silver out of silver nitrate and make mirrors! I did this in highschool chemisty, but my beaker is basically brown now. I don't know if it's an oxidative state (a patina) or somehow it form a nitrate in atmospheric conditons (the nitrogen tripple bond is >9 eV).

[fabimre]

I am a bit of a DIY'er and laid my own laminate floor panels.
For the Underfloor I used adhesive Aluminium tape, ultra smooth and reclective. That would be suitable!

[Kirillissimus]

You could turn the meter into a special one for measuring secret voltages inside secret circuits. Just remove all the polarizing films from the LCD, stick a piece of white paper to the back and wear polarizing glasses.

[jonsnell]

Good to hear the word Zebra pronounced properly.

[izimsi]

"the alignment does not matter", but every time I tried removing an LCD with a zebra strip, some of segments were then missing.
Maybe it just got dirty, but I don't think I've ever managed to reinstall it properly.

[alexisdrosopoulos]

I believe that this happened to the adhesive due to exposure to UV by sunlight. It's a common point of failure for old nintendo gameboys for example

[excavatoree]

Brings a tear to the eye. I've been down that road.

I'll mention that Fluke did change to the clear windows with no model designation, with the designation moving to the LCD surround, but they had retrofit kits for the older meters with a printed LCD surround and clear window. After installing the new surround, one could purchase a new window when necessary. Sadly, Fluke doesn't offer these anymore, but most just re-polish existing windows with good results.

I'll also mention that I've only had to change a handful of zebra strips, but it's important to put them in the way they came out if the contacts are the raised, solder type. These differ in height, and the connector takes a permanent "set" and won't make good contact if placed in a different location or orientation. At least one crazy person has had to try all 8 combinations (as it's obvious which side is toward the LCD0 when he forgot where they went and in what orientation.

[iamdarkyoshi]

Well now I'd be quite interested to see a troubleshooting session with the other meter, if nothing else just to see a damage report of what happens when you blow the ass out of it

[Richardincancale]

Try some polarising film from an old lcd monitor cut to shape?

[rmd]

Put a light source behind the backless LCD and make a projection meter!

[monkshoodtv]

Bit of mucking about. But how about using Kitchen foil as a silver backing with a bit of polarising film. Held together with some photograph mounting adhesive. The polarising film can easily be obtained from any lighting outlet especially Film and TV suppliers where it's a dime a meter. Just for fun.

[lookupfromdownunder]

I was in component level repair with Telstra 20 years. We had this prob with our Flukes. Fluke said it is because these are not Tropical Displays, which we need in Australia. They supplied us with replacement displays. Regards Norm in

[Standing-Wave]

Having Mrs. EEVblog explain the discolouration would be super interesting, along with why some plastics in older gear turns yellow.

[dentakuweb]

That was both informative and a repair which is what people like of course.
Years ago I didn't know how zebra strips worked then I looked at one closely and figured it out.