Recovery of an old Fluke 8020a with a bad LCD

[lowimpedance]

Hi
 This is my first attempt at posting so I hope the pictures attach properly.

 Just thought some may be interested in my rebuild of the LCD display on an old Fluke 8020a handheld meter.
What I did was to buy a 3.5 digit lcd (cheap) with through hole pins and then modify the plastic mount for the
old display so the new one would fit nicely and the slide in cover would keep it in place.
Next for the fun bit was to use wire wrap wire to connect the new LCD to the pcb pads where the old 'Zebra strip' was.
one of the photos shows clearly the old LCD module with the classic leaching of the older Flukes, making them totally
unusable.
 The calibration is in spec. and has been checked on a calibrator at work.
Some may ask why bother, the answer is because I hate to see a good meter end up in landfill and I got a fully functional
meter to add to the collection.
cheers
LowZ

[Kiriakos-GR]

Great job ...  

I bet that you will enjoy this link too.

https://www.eevblog.com/forum/index.php?topic=718.0

Welcome in the forum John ..

[Excavatoree]

Great idea.  These old meters (8020, 8021, 8022, ....) will last a while, but their weakness is the LCD, and stock LCDs and zebra strips are difficult if not impossible to find.  (and some are selling them for ridiculous prices.)

I'm a big fan of these meters, and also the idea of keeping something working.

[saturation]

Great job!  That series put Fluke on the map, one of the first most popular DMMs.

http://support.fluke.com/SW-Common/SW-Find_It.asp


http://www.fluke.com/fluke/usen/community/fluke-news-plus/articlecategories/rd/a+little+history.htm

[ElektroQuark]

http://support.fluke.com/SW-Common/SW-Find_It.asp

FLUKE says:

"Digital Library Fulfillment Center

# We are sorry, but the link provided to you to access this information is not valid.
# An automatic notification message detailing this problem was sent to the site administrator.
# Invalid Locator Format 4 - Invalid Document Number"

[saturation]

Sorry, try this:

http://support.fluke.com/find_it.asp?Document=2386856

If it doesn't work, the main page of the article, the link is at the bottom.  The article is a pdf file.

http://www.fluke.com/fluke/usen/community/fluke-news-plus/articlecategories/rd/a+little+history.htm

http://support.fluke.com/SW-Common/SW-Find_It.asp

FLUKE says:

"Digital Library Fulfillment Center

# We are sorry, but the link provided to you to access this information is not valid.
# An automatic notification message detailing this problem was sent to the site administrator.
# Invalid Locator Format 4 - Invalid Document Number"

[Excavatoree]

Sorry for the intrusion, but can you give us the source and part number of the replacement display? 

[Kiriakos-GR]

Sorry for the intrusion, but can you give us the source and part number of the replacement display?  

Yes I am second in the line for this request ..  

( it will be nice to know just in case that another similar needs to be rescued )

And also the cross connection schematic !!  ( if possible )  

About the tiny small cables as bridges , they can be found easily , inside of USB cables .. 

[Ernie Milko]

Excellent work. These are very good meters.
Did you manage to incorporate the low-batt flag?

[Vyper]

haha..I have one of those in the lab! It was/is a very good dmm. I rather liked them, I think they were manual ranging though. But good meters. Good luck sounds like a fun project. Think Ill get mine out of storage and see if it still works

[Kiriakos-GR]

Did you manage to incorporate the low-batt flag?

That's interesting , in such repairs , no one can do that ,
because there is no spare digits on the " generic displays ".

Only the genuine Fluke displays haves this "extra" ability.
 

[lowimpedance]

]Hi Kiriakos
 Nice thread on the 8010, 12, and 50. I have all these meters too. Excellent meters for small money IF you can get one with a good LCD. I have done a similar replacement job on my 8012 (bit more involved mechanically). Still economic with a 3.5 digit
 Replacing a 4.5 digit LCD though you might be better of contacting Fluke, but then you would be better of buying a new meter.
 Interesting to note that both the 8020a and the 8010 and 8012 use the old ICL 7106 as the lcd driver/ converter  disquised by a Fluke P/N.
EDIT: this turns out to be not the case as noted in the excellent thread 'OLD Fluke Multimeters', from DrTaylor of Fluke 8060a fame. The ICL7106 has some important range switching omitted.

Hi Ernie
 Yes I have been able to include the low BATT symbol since it was part of the LCD I used as a replacement. I have also checked it works by running the meter from a bench supply.

cheers
LowZ

ps will get the hang of this forum stuff with using the quotes and other tools etc as time goes on but was not confident yet in case I look like a total nooby

[Kiriakos-GR]

John  do you have any part number about the display that you had use ?
Or info about the source of where did you got it ? price etc..

As you can see , in this place we share anything , except of our wife's .. 

 

[lowimpedance]

Hi Kiriakos
 If you need to go down this path of repair then any reflective type 3.5 digit + LoBatt lcd from RS Components or Element14 will do.
For example the RS part number 215 6436  (Clover display or Varitronix). price around $10 Aust.
 The lcd for the 8050a would be too difficult with its extra custom annunciators to replace easily.
On a slightly different note with the handheld 4.5 digit version the 8062a if you come accross one of these cheap beware that its possible the minature electrolytics which the meter has a good number on its pcb are prone to leaking and causing considerable damage and possibly the death of the meter (speaking from experience).

Cheers
LowZ

[Kiriakos-GR]

Thanks for the tip   


link: http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=2156436

[Excavatoree]

Thanks from me as well.

[Ernie Milko]

Thanks a lot for the inspiration; I'll have to give this a go on mine when I get the chance.

[Vyper]

I found my old meter. I thought it was a 8020a but its a 8060A. It still works good! along with my simpson 376 RT AC VM.

[Vyper]

here is a photo!

I found my old meter. I thought it was a 8020a but its a 8060A. It still works good! along with my simpson 376 RT AC VM.

[saturation]

Some of your photos are a trip down memory lane, I see an older model orange colored logo B&K Precision function generator, it looks like it has missing knobs.  1 newer blue colored B&K sweep function generator is also in the photo.

[Vyper]

You're right Saturation! Its an older BK precision/Dynascan 3020 SFG. Range knobe is missing but it works great. My newer one is a BK 4017 SFG, Fluke 45 dual display bench dmm, a EZ-FC-7150 freq. counter. I have a BK 1590A analog scope I still use
A BK 1715 DC PS, BK1686 DC PS, BK1653A AC PS, BK1604A Isolated AC PS, Heath Zenith SP-2717 HV PS, BK 1650 Tri output PS, BK1805 freq. counter, Advantest R3267 Spectrum Analyzer, Etc, Etc,.. These are my personal tools. The agency I work for has equipment you wouldnt BELIEVE That I use in the lab. Oh well...One can only dream of owning them Like a Rohde&Schwarz R&S®FSU67 and a
Rohde&Schwarz SMR40 Microwave Signal Generators to name a few. But WAY outta my pay rang or anyone elses I can think of!!

[saturation]

The good news with that is you can test your home gear against stuff you have at work, its surprising how much lower cost gear can perform very well in select or many areas, but you need excellent test equipment to reference your home gear against.

You're right Saturation! Its an older BK precision/Dynascan 3020 SFG. Range knobe is missing but it works great. My newer one is a BK 4017 SFG, Fluke 45 dual display bench dmm, a EZ-FC-7150 freq. counter. I have a BK 1590A analog scope I still use
A BK 1715 DC PS, BK1686 DC PS, BK1653A AC PS, BK1604A Isolated AC PS, Heath Zenith SP-2717 HV PS, BK 1650 Tri output PS, BK1805 freq. counter, Advantest R3267 Spectrum Analyzer, Etc, Etc,.. These are my personal tools. The agency I work for has equipment you wouldnt BELIEVE That I use in the lab. Oh well...One can only dream of owning them Like a Rohde&Schwarz R&S®FSU67 and a
Rohde&Schwarz SMR40 Microwave Signal Generators to name a few. But WAY outta my pay rang or anyone elses I can think of!!

[sonicj]

murdered out 77/bn mod

[Excavatoree]

Ok, I have to know how you did that.  I know it has to do with reversing the polarization, but I'm guessing you'd have to either use a different LCD or somehow remove the polarizer on the stock LCD and add another that is rotated 90 degrees.

[sonicj]

 

-remove the front polarizer. i used alcohol and fresh razor blade. it takes some effort to remove w/o damaging the plastic polarizer.
-remove adhesive from polarizer. this step is the hardest. the glue/epoxy is pretty tenacious. i scratched the polarizer pretty good and sorta melted it trying different solvents. denatured alcohol and patience worked best. replacement polarizing film is available online if you screw up.
-clean the glass. remove any excess adhesive. wipe your dirty paw prints off everything. gloves and kimwipes at this point. i didn't spend as much time on prep as i should have as this is a dead meter and i was just experimenting.
-replace the front polarizer inverted. i used some polyamide tape to hold it down for the photo, but if i were doing it on a working meter i'd likely use a optical grade epoxy like norland 72 or similar.
-done.


i just ordered a swatchbook from rosco.... i want to play with some colors next! link

[Excavatoree]

I knew I kept those faded old 70 type displays for a reason!  Now I've got plenty to practice on.

[sonicj]

its easy. you gotta really try hard to mess up the front of the glass. the polarizer was surprising tough on this fluke. even if you mess it up, you can use the polarizer from another lcd or just order up some fresh film for a couple $. optical adhesives can be expensive, but aren't required. in fact, some of the polarizing films come with adhesive already applied.

you could also remove the back polarizer & reflector, replace with a transflective surface and then add EL film for backlighting. the fiber optic backlight stuff is balla'! 

easy/cheap way to add some bling/character to otherwise boring and dated gear!
-sj

[Excavatoree]

Thanks for the info.  I didn't realize how easy it was to remove the polarizer.  More importantly, I discovered that the "faded LCDs" that I had are fine - it's the polarizing film that deteriorates.   Reports of the demise of several of my LCDS were greatly exaggerated.   

[ModemHead]

Thanks for the info.  I didn't realize how easy it was to remove the polarizer.  More importantly, I discovered that the "faded LCDs" that I had are fine - it's the polarizing film that deteriorates.   Reports of the demise of several of my LCDS were greatly exaggerated.   

Add me to the this club.  I have an old beat-up 29-II with a badly faded display that I thought was a lost cause, but after removing the old polarizer and adding some new polarizing film, the contrast is restored!  BTW, I found that strong citrus solvent (specifically, "Goo-Gone" brand) helped in removing adhesive without damaging anything.

Many thanks to the contributors in this thread.  I've learned a useful new repair technique.

[Excavatoree]

The 29/76/79 LCD is almost impossible to find, so the motivation for being able to fix these is greater.  I found a gentleman selling the 21,23,70,73,75,77...type LCDs on e-bay and bought a lifetime supply (before his price went up, I guess as his stock depletes the cost rises) but I hadn't even considered that I can restore my 29s.

If you don't mind telling me, where is a good place to order polarizing film?  Does the stuff with adhesive work as well as using a separate adhesive?


FOUR YEARS LATER EDIT:  The situation about the 79 and 29 LCDs has changed.  Someone was selling  29/79 (maybe 76?)  LCDS on E-bay in massive quantities at low prices.   This was a "game changer" and these are now readily available and at lower cost.

[ModemHead]

The 29/76/79 LCD is almost impossible to find, so the motivation for being able to fix these is greater.

You can say that again. I picked up a broken 79-II cheap just for the LCD, but it turned out to be very easy to repair, so I just demoted the 29 to back-of-the-truck-seat-in-case-of-emergency duty.  It was usable if you held it at just the right angle.

If you don't mind telling me, where is a good place to order polarizing film?  Does the stuff with adhesive work as well as using a separate adhesive?

I got some of this from American Science & Surplus. It doesn't have any adhesive. I just cut a piece slightly oversized and let the bezel hold it down. Seems to work OK.  The only thing is that I had to turn it 45 degrees, so the cutting was somewhat wasteful.

[jwhitmor]

Beautiful, professional, job!   

I have been trying to find a way to salvage my favorite old Fluke 8020A for years. I bought it at a time when they cost "real dollars", and I used it to troubleshoot my first computer project, (which had 14,000 hand soldered joints). I have the through pin LCD replacement. Do you have any sort of circuit interconnect table or diagram you would like to share? If not, I will wait until I am snowed in for a couple of days, and use that time to figure it out (in between chucking logs into the fireplace).

Thanks!
J. R.

[lowimpedance]

Beautiful, professional, job!   

I have been trying to find a way to salvage my favorite old Fluke 8020A for years. I bought it at a time when they cost "real dollars", and I used it to troubleshoot my first computer project, (which had 14,000 hand soldered joints). I have the through pin LCD replacement. Do you have any sort of circuit interconnect table or diagram you would like to share? If not, I will wait until I am snowed in for a couple of days, and use that time to figure it out (in between chucking logs into the fireplace).

Thanks!
J. R.

 I must admit that I cannot locate the scribble that passes for a connection diagram, however you should be able to work it out easily from the 8020a schemattic  (fluke website if you dont already have), and your lcd datasheet. Note the main IC is similar to the ICL7106 which has plenty of data on the web, (curiously enough Intersil also made a reversed pin connected version which is luckily not common. I repaired an old Keithley with the more common 7106 doing a dead bug style wiring to get the connections right!). The only other point to make is the mechanical fitting, I was able to remove the right amount of plastic from the moulded plastic support so that the LCD sits on and could get the protective plastic cover to fit by milling it out in my workshop at work. So if you dont have access to something like that then you could use a dremmel etc very carefully to do the job, (and take your time). Solder all your wires needed to the pcb first, (wire wrap wire works a treat), then attach the LCD mount and connect each to the required pin. As long as you get the back plane right any other mistakes can easily be identified and corrected.
 When done the display will look better than the origional fluke in good condition, well mine does, ( I have other flukes to compare).
Good luck
cheers
LowZ

[jwhitmor]

Thanks for the great tips. I do have the LCD data sheet, but I figured the 8020A schematic was unobtainable. I will scrounge a copy, or use the generic ICL7106 pin-out to work out the details. The LCD fits everywhere except the bottom pins, so I will either drill holes for them, or mill off the bottom edge of the holder. If it is too thick to allow the factory cover to slide in, I will probably try using some thinner plastic sheet to make a new cover. The Fluke piece with the painted mask is 0.130 thick, so I have some room to fudge, and I will no longer need the exact pressure on the LCD that Fluke needed to make the elastomeric contacts work, so if I can fit it in it is sure to work.
I kind of wish everybody made a mirror image version of their IC's, because it would save me when I print and etch a PC board backwards!

Thanks again,
J. R.

[jwhitmor]

URL for FLUKE 8020a SCHEMATIC:
http://assets.fluke.com/manuals/8020A___imeng0000.pdf

complete manual scan in .pdf with the schematic in section 7 (near the end).

[jwhitmor]

I followed the lead of "lowimpedance" and once again have a working Fluke 8020A. The part I used (in the U.S.) was a "Lumex LCD-S3X1C50TR/A"  (0.5 high, 3.5 digit, LCD, glass). It fit precisely between the side edge guides, and under the factory cover, after some milling away of interfering plastic on the display holder. The project took (me) about 5 hours to complete.

Here is a photo of the new LCD powered up, with the old "blackened" LCD lying just below it.


A photo of the completed assembly, along with some of the essentials to do the job, and the old parts no longer needed.
(the IC in the background is from another project)


I can post a listing of the wire connections (in .pdf form) if anybody else wants to try this.

I never would have attempted this without the inspiration "lowimpedance" provided.
J.W.

[Kiriakos-GR]

congrats ... jwhitmor

You did a fine job with it..
Did you connect and test, the low-batt indicator ? ( on the LCD)

[jwhitmor]

Yes, the "LO BAT" indicator in the upper right corner of the Lumex LCD comes on when the battery supply falls to ~7.5 VDC. The LCD also has an "OVER" (over range) indicator, but there is no discrete output from the 8020A logic to drive it. Instead Fluke used a unique "stacked electrode" arrangement in their LCD, where the over range indicator shared an output with the half digit ("1") indication. It looks like they did a logical "AND" (in their LCD) with the drive for the three full digits, and if the three full digits AND the OR/1 output were both driven (high), it displayed a "1" but if the full digits were blanked (low), AND the OR/1 output was driven (high), it displayed the over range indication. Not sure exactly how it worked, or why they did it, but my meter still indicates an over range by blanking out the three full digits, which is enough for me. I try not to over range my meters anyway 

[lowimpedance]

Excellent job JW
 Your meter looks pristine in the photo, (not 'yellowed' like mine).
Job well worth it, now another 8020 ready for another 20 years! .

Cheers
LowZ

[jwhitmor]

Actually, mine was turning yellow too, but while I had the PCB out of the case, I scrubbed the case with a soft rag and some automotive cleaner wax. I went really easy on the front panel markings. The LCD came from an on-line division of Farnell named "Element14." It was less than 4 $US (plus $5 for shipping). The really funny part is, that none of my new "genuine Fluke" test leads will fit the 8020A. The rubber skirt that surrounds the banana plug is a little too big. I have the originals "somewhere" and if not, I will put some long straight banana plugs on a new set.

[david77]

Good job!
Another Fluke meter saved from the skip   .

They may not be compliant to current safety regulations, but I'd still trust them more than any cheapy
China meter. I bet the 8020 survives 230VAC on the ohms range... no don't try it  .

[Kiriakos-GR]

The really funny part is, that none of my new "genuine Fluke" test leads will fit the 8020A. The rubber skirt that surrounds the banana plug is a little too big. I have the originals "somewhere" and if not, I will put some long straight banana plugs on a new set.

haha no-shit ..  

Same story also with the the desktops 8010A & 8012A ,
and only the latest 8050A will accept the latest Fluke leads, the ones that work with the 87V and 28II.

I did a long investigation, and found nothing (as an old product code for them).

straight banana

Yes the only solution , but avoid the very cheap ones with rubber cover.  

[jwhitmor]

I do not remember the 8020A having the HV fuse which seems to be standard in the new fluke meters, but I do agree with David77. A guy I knew used a cut-rate meter to troubleshoot a light fixture on a small airport runway. Guess he did not know they run at high voltage, because the meter flashed over internally, and blew the cover to pieces. He was OK because it was cold outside, and he had gloves on. The meter, and his composure were both destroyed. Next time he works on HV, he will probably try using his "Wiggins" tester.
J.W.

[Kiriakos-GR]

The desktops 8010A & 8012A & 8050A , they do have High voltage Fuses in them.
But it is on the PCB , they also have glass fuses at their face plates ... as primary.
Plus an third fuse after their transformer ..  

I bet that high level of humidity helped in such HV accident.

This is another good reason , of why I feel very nice, by having next to me the waterproof 28II .

And I will continue to thanks our Dave for that, as long I live..  
  

[alm]

The fuse is only used for current measurements, which are typically not used when troubleshooting light fixtures, except by mistake. Sounds like just bad design or bad reading of the specs by the user, if it was not designed for this over voltage.

[donbrenrik]

jwhitmor; that was great replacement.  Ordered 2 LUMEX lcd units from Mouser to repair my 8020A used in
80s when I worked for data general here in MA area.  Would appreciate it very much if you cound email me PDF for wiring connections.  I have LUMEX Data sheet and Fluke pdf manual.  Thanks again for the fine article and pictures of the 8020A; as well as the LCD part number.  Bye for now.

don71bren@verizon.net

[lowimpedance]

jwhitmor; that was great replacement.  Ordered 2 LUMEX lcd units from Mouser to repair my 8020A used in
80s when I worked for data general here in MA area.  Would appreciate it very much if you cound email me PDF for wiring connections.  I have LUMEX Data sheet and Fluke pdf manual.  Thanks again for the fine article and pictures of the 8020A; as well as the LCD part number.  Bye for now.

don71bren@verizon.net

Hi Don
 See below my origional response to JW at the time when he repaired his fluke. Note the IC used by fluke is similar to the INTERSIL ICL7106 LCD driver, so use that data sheet in combination with the Fluke manual to get the PCB connections. Have a look at my pictures in post 1. The mechanical mod to the LCD housing to accomodate the new LCD is most likely the hardest part. Take it easy dont rush and before you know it the 8020 will be ready for many more years of service. Have fun, and if JW is reading this and can forward a wiring diagram well all the better.
Just recently I have aquired another 8020a with a dud display(at the right price of course  ), a job for a rainy day ----

LowZ
 

Beautiful, professional, job!   

I have been trying to find a way to salvage my favorite old Fluke 8020A for years. I bought it at a time when they cost "real dollars", and I used it to troubleshoot my first computer project, (which had 14,000 hand soldered joints). I have the through pin LCD replacement. Do you have any sort of circuit interconnect table or diagram you would like to share? If not, I will wait until I am snowed in for a couple of days, and use that time to figure it out (in between chucking logs into the fireplace).

Thanks!
J. R.

 I must admit that I cannot locate the scribble that passes for a connection diagram, however you should be able to work it out easily from the 8020a schemattic  (fluke website if you dont already have), and your lcd datasheet. Note the main IC is an ICL7106 with plenty of data on the web, (curiously enough Intersil also made a reversed pin connected version which is luckily not common. I repaired an old Keithley with the more common 7106 doing a dead bug style wiring to get the connections right!). The only other point to make is the mechanical fitting, I was able to remove the right amount of plastic from the moulded plastic support so that the LCD sits on and could get the protective plastic cover to fit by milling it out in my workshop at work. So if you dont have access to something like that then you could use a dremmel etc very carefully to do the job, (and take your time). Solder all your wires needed to the pcb first, (wire wrap wire works a treat), then attach the LCD mount and connect each to the required pin. As long as you get the back plane right any other mistakes can easily be identified and corrected.
 When done the display will look better than the origional fluke in good condition, well mine does, ( I have other flukes to compare).
Good luck
cheers
John

[jwhitmor]

donbrenrik,
I have been away from the eevblog, and apologize for the delay. I Emailed the information to the address you provided, and will try to attach it here as a zipped .pdf file. The plastic support under the original LCD is too deep and a little too tall to fit the new LCD under the cover glass. I removed the plastic that got in the way with small files and a Dremel tool. There was not much holding a couple of the legs to the support when I was done, but it has worked very well so far. It may be possible to save a bit more plastic on top, by shortening the legs a bit, but that may present some problems too. There is room under the plastic support to route some of the individual wires that replace the ribbon cable. Just be a patient and neat as possible. I do not believe the "Over-Range" indication can be made to work without additional logic circuits, but the digits "blank" on an over-range, so you know if (when) it happens.
Cheers!
jwhitmor

[Kiriakos-GR]

Great work jwhitmor 

I saved one copy of your PDF too.

[SgtRock]

To All:

--Great work. This post contains a wealth of info on old fluke displays. I saved an old 77 by replacing the DA chip and the elastomeric conductors. I got the new grey rubber (instead of pink) conductors and a NOS DA chip from Fluke for $25 shipping included.

--Now, seeing what you fellows have done with old LCD displays, I cannot wait to get my hands on an old Fluke meter (cheaply) that needs this kind of work. Special thanks to Kiriakos, who like Odysseus, is never at a loss.

"The difficulty is not so great to die for a friend, as to find a friend worth dying for." Homer
Best Regards
Clear Ether

[lowimpedance]

donbrenrik,
I have been away from the eevblog, and apologize for the delay. I Emailed the information to the address you provided, and will try to attach it here as a zipped .pdf file. The plastic support under the original LCD is too deep and a little too tall to fit the new LCD under the cover glass. I removed the plastic that got in the way with small files and a Dremel tool. There was not much holding a couple of the legs to the support when I was done, but it has worked very well so far. It may be possible to save a bit more plastic on top, by shortening the legs a bit, but that may present some problems too. There is room under the plastic support to route some of the individual wires that replace the ribbon cable. Just be a patient and neat as possible. I do not believe the "Over-Range" indication can be made to work without additional logic circuits, but the digits "blank" on an over-range, so you know if (when) it happens.
Cheers!
jwhitmor

 Handy to have JW. Coincidently I have just finished this week the replacement of another dud LCD on my second unit (using a LUMEX lcd this time), and found my old wiring diagrams.
Yours is MUCH neater!. Just to note the 8020a only used the '1' and the last three digits blanked to indicate an overange condition (see manual page 2.3 parra 2.18).
 Of course my 8020's LCD's were so bad I could not make out the digits let alone any other announciators.
regards
LowZ

[E.Stern]

It's been a while since the last post in this informative thread, and I'm thankful I found it today.

My employer was a longtime user of the 8020A. He's retiring in the coming year and I have his original 8020A, gifted to him by his previous employer already. (see the nameplate on the unit). I'd like to fix it and give it to him again at his final retirement.



Uploaded with ImageShack.us


The LCD is toast, as appears common on these units.

I'll follow what I'm learning so far on the thread, but I have a question. Are you all replacing both the LCD screen and the IC, or just the LCD?

I'm handy enough to attempt the repair on the dead unit, but I don't know enough about electronics to understand some of your lingo. I am comfortable to order a Lumex LCD as spec'd earlier in the forum. That may be all I need, plus some of the soldering expertise from the electronics guys in this building (it's been a decade since I was in school for it, and my job doesn't require me to solder anything-boats are all crimp.)

[PaulAm]

Just ran across this thread, great info!

I have an old D802 with a bad LCD.  I bought an 8020 off of ebay to use for parts, but it turned out that meter works perfectly.  So now I have a way of fixing the original which has some sentimental value.  It was the first piece of pro level test equipment I ever purchased.

[lowimpedance]

@ E.Stern, highly unlikely to need the main IC replaced (its not the common part ICL7106 by the way). Just read all the info already posted and it should be down to just CAREFULLY fitting the LCD mechanically to the plastic mount the original sat on, this requires some material to be machined away for the LCD pins to sit properly, (use a dremel etc if you don't have access to a machine shop!). The rest is just wiring using thin single core wire like wire wrap wire for example. Once the job is done and wired correctly, (a crossed wire is likely at first attempt!!), that area of the meter will never need touching again.
Good luck
 LowZ

[TerraHertz]

Interesting thread! I have an old Fluke 8020A and 8022A, which both still work EXCEPT that the 8022A has a couple of the decimal points on the LCD permanently on. I've tried disassembling it, cleaning the LCD edge, the zebra strip and the PCB, reversing the zebra strip, visually checking for any board shorts, etc, but no luck. Without the circuit I couldn't think of anything more to do, and decided it was probably a fault in the main chip anyway.

So, the schematics are available! Cool. Time to have another go at it.
I don't suppose anyone else has ever had this problem, and fixed it? See pic.

Edit: FWIW, I recall hearing long ago that sunlight was bad for LCDs, so I always avoided leaving these meters in sunlight. This might be why their LCDs are both still perfectly good.
Maybe this doesn't apply to modern LCDs?

Edit2: Dammit. All the amazing 'restoration of old test gear' threads here - cannot unsee. Now I feel guilty every time I look at some of my old gear and realize it could do with cleaning.

[ModemHead]

Interesting thread! I have an old Fluke 8020A and 8022A, which both still work EXCEPT that the 8022A has a couple of the decimal points on the LCD permanently on. I've tried disassembling it, cleaning the LCD edge, the zebra strip and the PCB, reversing the zebra strip, visually checking for any board shorts, etc, but no luck. Without the circuit I couldn't think of anything more to do, and decided it was probably a fault in the main chip anyway.

There's a CD4030 quad XOR gate (U7) that drives the decimal points and the lo-bat annunciator.  The steady-state decimal point logic signals come from the range selector switches and then are XORed with the LCD backplane clock to get the required 50Hz bipolar drive signals for the LCD.

Check that there is 5V or so from U7P7 to U7P14, because Vss (negative supply) for U7 is generated from the ICL7106 and if that failed there may only be about 2.5V or so.

DP1 is U7P13.  DP10 is U7P6.  DP100 is U7P8.  Only one of these signals should be logic high (with respect to U7P7).  If all three are high, then something is wrong with the range selector switches.  If not, then U7 may be bad.

[TerraHertz]

Yay! Fixed. It was the 4030. Quite a strange failure mode - two of the outputs were not XORs of their respective inputs, but a much more complex function of multiple inputs, including some intervals of 'linear' not digital output.  But still roughly square waves as they should be, except at half the frequency of the LCD drive square wave. Some kind of odd internal defect in the chip that managed to produce a div-by-two circuit? Not just blown outputs or inputs as usual with 4000 series logic.

I don't know why I had assumed no schematic would be available for this. Lazy I guess.
Anyway, given the schematic, easy. And I cleaned the case too. Nice to have the old thing back.

[ModemHead]

Excellent.  And nice job on the clean-up. 

[E.Stern]

On disassembly I noticed that the glass over the existing LCD on the 8020A was gripped so tightly by the plastic tabs that it bowed. It puts more pressure on the edges of the LCD via this bowing. Would the point-loading on the edges of the LCD screen be an issue for failure?

Also, with the new LUMEX LCD screen that I'm preparing to order, should I expect the original polarizing glass to fit back in place?

Thanks for the vote of confidence. I have a senior computer tech on hand for the soldering challenge, and I'll post once the job is done.

Cheers from Newfoundland

[lowimpedance]

@TerraHertz - Nice and shiny  , Its nice to see so many of these old timers still chuuging along out there!
 
@E.Stern - If you are referring to the clear acrylic, (perspex), sheet that holds the LCD in place ?! , then when fitting the new LCD (with pins!!) , just make sure this 'perspex sheet' is a good sliding fit and not a tight fit , when modifiying the plastic mount . Most definately does not want to be tight!. Yes its a good idea to retain this window for safety aswell as mechanical protection for the LCD.
good luck
LowZ

[PaulAm]

In a similar vein, I ran across this site:

http://www.spurtikus.de/basteln/repair/fluke_8010a/index.html

where an 8010 was repaired.  It's in German, but google does a pretty fair job of translation.  He has a nice table showing the pins/connections.

[ModemHead]

I recently performed this repair on an 8020A and documented the process.  Photos and write-up are available at http://mrmodemhead.com/blog/fluke-8020a-lcd-replacement/.

[lowimpedance]

I recently performed this repair on an 8020A and documented the process.  Photos and write-up are available at http://mrmodemhead.com/blog/fluke-8020a-lcd-replacement/.

Very nicely documented repairs, not just the 8020a but also the 'others' too. Lots of nice pic's.
I too have an 8062a which suffered the same 'electrolytic' fate as yours. I still have on going prob's. with the elastomeric strip.
 Again , nice web site.

[ModemHead]

Thanks for the inspiration.  And yep, 8060A electrolytic problems seem to be almost guaranteed. Hope you get yours sorted!

[ElektroQuark]

Nice blog ModemHead. I have just bookmarked it.
A suggestion: can you embed the images? Having to load them while reading stops the joy.

[retiredcaps]

Not to get off topic, but I actually prefer the thumbnails.  It gives it a cleaner look and makes for better printing.

[ModemHead]

Nice blog ModemHead. I have just bookmarked it.
A suggestion: can you embed the images? Having to load them while reading stops the joy.

OT: Thanks.  I would hate to de-rail this fine thread with a discussion of my meager blogging skills. Always open to suggestions via PM/email though. Suffice it to say I have not yet discovered a 'perfect' way to present detailed photos and commentary at the same time within the Wordpress framework.

[PA4TIM]

Fixed my 8022 a few years ago. Very easy, only a few euro from Conrad. To bad I could not find a suitable display for a Philips.
http://www.pa4tim.nl/wp-content/uploads/2010/11/DSC_3600.jpg     
http://www.pa4tim.nl/wp-content/uploads/2010/11/DSC_3601.jpg

[PaulAm]

Just finished my 802, that was an easy fix :-)

I used wirewrap wire on LCD pins 1-20, hot glued to the carrier and then soldered to the board contacts so those wires would all fit under the display.  Added stranded wires to the rest of the PCB contacts, mounted the display then soldered the wires to the LCD.  Made for a fairly neat repair.

I'm very happy to get the old soldier back on my bench.