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| Fluke 8840A/AF 8842A VFD Display Replacement |
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| bdunham7:
I've been working on a way to replace the faded or broken displays on the Fluke 884x series meters and I have a half-assed working prototype. Before I go another round with it, I'd like some input from those of you that might want one and possibly some advice on sourcing some better parts. The current version v1 uses individual 0.56" 7-segment displays and 2x5mm individual LEDs. This is not a drop-in replacement at the moment and it requires a bit of nibbling on the front housing assembly and it requires some soldering, bodging and IC replacement on the main board. The reasons for the nibbling is that the digits are larger (wider mostly) and there isn't room for the annunciator LEDs without squishing them very tight. As is is, the annunciators are going to be smaller than the original. The first question is color. I have 8 test boards since DK Red somehow doubled my 4-board order. I have a red version, a blue version and enough parts for a green version, although I think the green will be too dim under the bezel. I think the red one is the clearest and best looking, although unfortunately the photo seems blown out and doesn't show the nice deep red that is actually there. The digits can be read clearly from 15-20 feet away. The annunciators are another matter, and one possibility would be to use different colors so that once you learned them, you would know what mode the meter was in without actually needing to read the text of the annunciator. Any thoughts on color combos? The next question is what the priorities should be. Is avoiding any cutting worth reducing the display size further? Should I use smaller digits so as to make the annunciators larger? Do people want a lower-cost kit that can be customized for color or a high-quality ready to install product--or even the whole job done as a service? One issue is the half-digit and +/- sign which is a bit clunky right now. I tried to find a "+1." or a "+1.8." display and matching "8.8." or 8.8.8.8." displays, but could not source them. I found a listing, shown in a photo below. My other options are to keep the design as is and perhaps tilt the "+" sign to match the digits and reduce the size with the mask that I haven't made yet, or I could actually saw one of the digits and remove about 40% of the left half and do a bit more nibbling and adjust the mask so that it looks good. If I'm doing a one-or-two-off project that would be fine, but it's too much work for shipping product. I'm not sure if a typical kit buyer wants to do that much work either, but that a question that can be answered here. As it stands, I can probably produce a kit that will work and look nice but will require complete disassembly of the meter, removing and soldering PDIP ICs, nipping leads and running two bodge wires, nibbling the front housing and perhaps sawing a digit in half as well as soldering the through-hole components onto the board. I would sell it with the SMT stuff already on there. Alternatively, I might be able to produce a more expensive kit that would require removing 3 ICs, soldering in a neat replacement module or modules and then installing a complete display module, possibly without any nibbling of the front housing. Comments welcome, even if only to let me know that you might want one. |
| Black Phoenix:
My suggestion - Provide 3 stickers (or a full screen one with a middle insert that you can remove after application) to apply in the plastic front panel were the lettered options that were replaced by LED on the replacement screen. Not that who have one don't know what each means by practice but new users will not know. Also make sure that the stickers have a strong enough glue but not as strong that to remove it is a bitch and left residue behind. Parts for this equipments start to get rare and expensive, so anything that looks like stock and can be removed without damaging anything is a god send. |
| tautech:
Or you can 3D print the annunciators as Defpom has here: https://youtu.be/mUhtBLLV6iA In a later vid he got a dual extruder 3D printer and they came out quite good. :) |
| SilverSolder:
Really cool project! Red is the way to go... I almost feel like I should get one of these meters just for this cool display... You could probably get a sticker made for the lettering, that would be awesome - perhaps black vinyl, with cutouts for the writing, and white vinyl behind the letters? |
| bdunham7:
--- Quote from: tautech on April 26, 2021, 01:28:20 am ---Or you can 3D print the annunciators as Defpom has here: --- End quote --- Yes, I fully intend to make a 3D printed part that will separate all the LEDs and then a printed or laser cut front that actually replicates the lettering of the original display annunciators--so no stickers or such on the outside. I also need to manage the diffusion somehow so that they look as good as the digits do. The only issue there is that they are going to be smaller than the originals just because there isn't enough space, so I thought color coding them might be nice. The board is nowhere near perfect--I was tweaking it for a while then I decided to just send it out so that I could verify that it worked electrically and then solve the mechanical issues that arose. It works--the LEDs are even and no ghosting, so one more round and it should be a product. |
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