EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: bd139 on November 10, 2018, 11:14:01 pm
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IMPORTANT: if you do this, make sure you have the pinout for your display handy an the 8010A service manual and you read it end to end. This entire job is painful and frustrating. If you can, find a donor meter for a display and save yourself a few hours.
Got a Fluke 8012A for just over a tenner on ebay with a knackered display. This has low ohms so is handy for tracing out shorts and measuring shunts etc. I have an 8010A already.
Cleaned all the crud off it and it looks reasonable apart from the display:
(https://i.imgur.com/Nc4TShP.jpg)
Thought it was a mains only model but cracked it open and found battery box in it. This was removed as were the batteries. In these, there is an LM317 configured as a current source to charge the NiCd cells that were originally present. I converted this into constant voltage by cutting the regulator adj line, jumping the current setting resistor and using a 240R/330R voltage divider centered on the ADJ pin to out/ground. This gives constant voltage mode of around 3V. This is just above the 2.8V of a fully charged set of NiCd cells.
(https://i.imgur.com/XnZYH38.jpg)
(https://i.imgur.com/oDJMNd2.jpg)
At this point I noticed it was a bit slow to start up. After looking closely at the electrolytic capacitors, a couple had leaked electrolyte. All the capacitors were replaced instantly as a precaution.
(https://i.imgur.com/xIcpFh7.jpg)
Body count:
(https://i.imgur.com/np132C3.jpg)
Working nicely after that.
On to the display. A standard 3.5 digit LCD module fits nicely in these. I used a Display Elektronik DE113-RS-20/12.2 from bitsbox.co.uk (merely £4)
To replace the display requires some patience. The front panel of the meter was removed and the old display was removed with the zebra strip. As you can see the new display looks nothing like the old one so it's Kynar time:
(https://i.imgur.com/hTe81NN.jpg)
The display assembly needs modifying to fit the new LCD. Remove the two supporting strips from the rear of it and round off the inside edges.
Before:
(https://i.imgur.com/uPu0Vg9.jpg?1)
After:
(https://i.imgur.com/xCQUkje.jpg)
Then fold the LCD pins back on themselves like this:
(https://i.imgur.com/TgirYIF.jpg?1)
Then test fit it into the display assembly:
(https://i.imgur.com/6z02myP.jpg)
After that, the hard bit. Apply Kapton to the back of the LCD to protect it from solder blims and write the pin numbers on the kapton. Refer to the LCD datasheet for the module that you picked and solder an 8 inch (yes that long - I did mine slightly too short) piece of Kynar to each in use pin. Heatshrink the pins. Don't try and do it without heatshrinking - it's a world of pain you don't want to get into. Feed each half of the LCD's kynar wires thorough the display assembly's two holes on the rear.
IMPORTANT: after each wire you solder on, write the pin number of the wire on the kynar so you know where it goes later! How do you do this? Binary encoded as dots and dashes where dot = 1 and dash = 0. -.--. on the end of the wire means wire 22. Saves a lot of bleeping out and bleeping language later.
NOTE: there is a wiring error here. Check your instructions not my picture. pin 3 is missing and backplane pin 40 was disconnected eventually
(https://i.imgur.com/SvZAtgj.jpg?1)
Now kapton over the edge of the display connector on the board.
(https://i.imgur.com/9aMTyK4.jpg)
Next TRIPLE CHECK that you got all the wires out that you need and that you labelled them all. I didn't and had to throw an hour away rebuilding it.
Put the display module back into the meter and put the front panel back on and route the wires around the edges of the display module:
(https://i.imgur.com/DiIeynN.jpg)
Then wonder what unholy hell you've left yourself to deal with. I've started wiring here.
(https://i.imgur.com/YtUWeHv.jpg)
Wire everything according to the pin numbers correlated with the Fluke instructions. If you made the kynar too short (I did) it may not reach to some pins so you'll have to extend it. Then tie down the resulting Cthulhu with a couple of cable ties.
(https://i.imgur.com/GG6FfjF.jpg)
If you screwed up it will then look like this and you will have to go and bleep it out with a meter. :palm:
(https://i.imgur.com/phMzRIT.jpg)
After 40 minutes of debugging, it works:
(https://i.imgur.com/Y6yoU3U.jpg)
At this point treat yourself to a nice drink and promise yourself you're never going to do this again. Until the next time (this is the third one of these I've done).
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Beautiful job done there, looks totally original from the outside and is so much clearer than the other meter, me thinks you should do the same mode to that one as well and bring it into line and also extend its life.
Just a thought, have you ever tried it with the original zebra strips instead of having to solder those Kynar cables?
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Ouch, that IS ugly to do but if the display is FUBAR you really have no choice (Unless you have a parts mule).
Thanks for posting. :-+
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Beautiful job done there, looks totally original from the outside and is so much clearer than the other meter, me thinks you should do the same mode to that one as well and bring it into line and also extend its life.
Just a thought, have you ever tried it with the original zebra strips instead of having to solder those Kynar cables?
The new display is entirely different to the old one so that wouldn’t work.
It looks much better but I’m not going to fix the other one until it breaks
Ouch, that IS ugly to do but if the display is FUBAR you really have no choice (Unless you have a parts mule).
Thanks for posting. :-+
Very ugly but it works.
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I'll give you $50 for it. :-DD
mnem
Shipped. :P
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Hahahaha :-DD
That’s being buried with me :-DD
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All i have to say to this is twofold, first; excellent job! Really well done. Second, may Fluke have mercy on my soul, i'm staring down the barrel of having to do this to my 8010A. :-DD |O
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Excellent work, bd139. The 8020A is a bit more forgiving but I followed modemhead's procedure to the "T" and ended up wire wrapping instead of soldering (I was also afraid to birn the LCD). There was a lot of cursing and frustration so typical of wire wrapping, but it was totally worth it when I gave it to my dad. (It ended up coming back home after he passed away, though).
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Excellent Cthulhu wrangling there, bd! The new display looks better than an original. The digits look a tad larger, even.
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Excellent job! Really looks terrific.
It never occurred to me that one of those ubiquitous standard displays might be used.
Some of my 8050s have knackered displays, too, but the 3.5 digit modules won't do there. I know there's also 4.5 digit ones, but they might be too large.
After converting an 8050 to LED (absolutely shitty work), I know what you mean by "never doing this again". ;)
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Nothing ugly about that. It looks beautiful to me. :D
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I don't know for sure but I think that comment was about the bunch of cables inside which there is no answer to because the original traces do not match the connections on the replacement display. :popcorn:
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The whole thing is ugly.
I found a company about a year ago in China that makes custom LCDs in the same form factor so this could be an option too. The old Fluke meters have a standard size glass laminate so the only customisation is the edge connection and pin out. Unfortunately their English was as bad as my Cantonese which only stretches to insults so I sort of gave up. Prototype cost was around $30 for one display going down to $5 in quantity 100. Less for more.
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I'll give you $50 for it. :-DD
mnem
Shipped. :P
Hahahaha :-DD
That’s being buried with me :-DD
As if there were any doubt of that... :-DD
The whole thing is ugly.
I found a company about a year ago in China that makes custom LCDs in the same form factor so this could be an option too. The old Fluke meters have a standard size glass laminate so the only customisation is the edge connection and pin out. Unfortunately their English was as bad as my Cantonese which only stretches to insults so I sort of gave up. Prototype cost was around $30 for one display going down to $5 in quantity 100. Less for more.
I dunno about that... I think there's a certain kind of beauty in it, in an existential sense.
A) It has the beauty of form following function. Also, you gave up some of your most precious resource: time, just to 2) be able to say you could do it, and C) to save a good instrument that was destined to wind up in the landfill for no other reason than its makers were short-sighted about one single aspect of its design. That is the essence of TEA. ;)
But yeah... it would be awesome if you could get one of our Asian cohorts to make a replacement for a reasonable price. I'd think target should be right around $7ish, which, being as cheap a bastahd as I am, means the market could probably bear as much as $9-10 a copy.
mnem
Besides... who doesn't love a little electric spaghetti with Kapton sauce every once in a while? ;)
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That is a beautiful repair job.
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Nice job, thanks for the pics and detail. Nothing ugly about the result :-+. Id say its now good to go long after you'd have forgotton what it was for :D :P.
I quite like these old timers and given that no one seems to want them its a cheap way to get a decent enough meter.
Of the 5 various models of these series I have all have had dud electro's slowly eating away the PCB,
so yes when ever another enters the pile, the caps are first thing to go.
Also my 1st post on joining here way back in 2011 was an LCD repair to a 8020a
https://www.eevblog.com/forum/chat/recovery-of-an-old-fluke-8020a-with-a-bad-lcd/ (https://www.eevblog.com/forum/chat/recovery-of-an-old-fluke-8020a-with-a-bad-lcd/)
and its still going strong.
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Great project :-+
Sorry for my english. What word "Kynar" mean?
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Great project :-+
Sorry for my english. What word "Kynar" mean?
Kynar is a specialty wire, the kynar it was named after is the material used for insulation. Another name for the same thing would be wire wrap wire.
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It’s brand name for Teflon coated wire. Difficult to burn it while soldering :)
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Ahhh :-DD Is it simple teflon coated wire? Thanx :-+
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It is but is very thin solid core stuff for wire wrapping and fixing stuff (bodging)
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You can also get coloured wire wrap wire, would have helped with the identification of the wires, I have a drum of multi coloured stuff incase I ever get involved in stuff like this or need to bodge a broken trace etc.
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I just write the number on the wire in binary :)