EBAY: LED Display Module FLUKE 8840A/42A (DIY Kit) replace broken, damaged VFD

[AHOL]

This is an updated post.
The information corresponds to the modified module.
Only + 5V power supply is used.
The problem that was discussed up to 8 post is REDACTED. Fully working.


Hello All! That will be my first topic here.
Immediately I apologize for my English, I use Google translate.
I present to your attention LED DISPLAY MODULE FLUKE 8840A / 42A (DIY kit).





This story began a year ago, like many of you, I bought a FLUKE 8840A on eBay with a broken display.
The search for solutions to replace it did not lead to special results.
It was decided to develop our own LED module with a custom LED display.

ASSIGNMENT
This LED display module can be used to replace your broken, damaged, cracked, unusable, etc. VFD (itron CP2067A ) of FLUKE 8840A and 8842A multimeters. (FLUKE PART NO. 728873(FLUKE STOCK NO. 680843)).
This LED display module is intended for hobbyist simulation of various measurement devices, as well as for educational purposes, and provided AS IS as a DIY kit.
In addition, this display module can be used in electronics hobby projects, where a 5.5 seven-segment display with indication of additional characters is required.

DESCRIPTION
The LED display module is designed as close as possible to the original and does not require any modification to the multimeter. The module is mounted in place of the dismantled non-working VFD display.
The control scheme for one segment is shown in Fig. 1.



Fig.1

This module uses a custom-made, industrially produced 7-segment display.

BASIC TECHNICAL SPECIFICATION



BOM



FRONT PANEL DESIGN AND ALL LIGHT ON SEGMENT FEATURE



Pin assignment



Before shipping, each module is assembled (excluding the pin header) and tested. I guarantee a long service life provided that the consumer observes the conditions of transportation, storage and installation.
This kit has been tested with FLUKE 8840A and FLUKE 8842A multimeters.

INSTALLATION




















Photo of the installation in full resolution follow the link
https://drive.google.com/drive/folders/17eKHPnh537Mgt9A4NKM6ya5zAWMvPNiQ


I am the developer and sole producer of this module.
All other solutions on the market use the module purchased from me.
I only sell on eBay under a nickname:
grudn_2015


My shop on eBay:
https://www.ebay.com/str/aholstore

The price at which I sell the module (without shipping and taxes): - $34.4

The LED display module is sold here:
https://www.ebay.com/itm/155853129116


Thank you for your interest!
Good luck with your research and measurements!

[bdunham7]

That looks really good, but where does it derive the LED power from?

[AHOL]

Hello bdunham7! Saw yours display too, not a bad job either.

Driver VFD delivers current up to 40mA

[bdunham7]

OK, you run the LEDs directly from the VFD driver?  The problem I ran into is that the VFD is driven off of the +30V front end amplifier supply and when I tried to power the LEDs from it, the +30V power supply became overloaded and dropped out below regulation.  The problem is the power supply, not the VFD driver chips.  This will cause the meter to not function properly at certain inputs.   So I think you have a problem there.  I solved that problem by modifying the main board, but my main obstacle at the moment is getting the LED display itself made up.  If I had a complete LED  display, I'd have a complete solution and I can use 30mA (or more) LED current drive in my setup. 

[bdunham7]

Also, where do you get your ground (V_ss) since there is not a ground (Digital LO) connection to the display driver board?

[AHOL]

Yes, you are right, there is a voltage drop, but +30V is used to power the VFD driver and the U306.
But here is what the instruction requires in order to pass the calibration and work correctly:

To test load sources, set the 8842A to 20V and measure the voltages across TP301, TP302, and TP303. TP301 should be 6.3V (typical) above TP302 and TP303 should be 6.2V (typical) below TP302.

When the module is running, these parameters are normal.
And the multimeter passes a self-test.

Vss is the VFD power winding.

[AHOL]

Continuation of the post about power U306 (LT1012)

Aalmost the same and for AD547 who has it installed.

Data from spec:

[bdunham7]

Yes, you are right, there is a voltage drop, but +30V is used to power the VFD driver and the U306.
But here is what the instruction requires in order to pass the calibration and work correctly:

To test load sources, set the 8842A to 20V and measure the voltages across TP301, TP302, and TP303. TP301 should be 6.3V (typical) above TP302 and TP303 should be 6.2V (typical) below TP302.

When the module is running, these parameters are normal.
And the multimeter passes a self-test.

I'm sorry to say that I think you've made a grave error (big mistake), but you may get away with it for a while depending on exactly how much current your LEDs draw.

The +/- 30 volts are required because the circuit (picture attached) floats the supply voltage for U306 up and down with the output, so the + supply would vary up to as much as 26.3 volts or so.  Testing this without an input won't reveal a shortcoming in the +30V supply.  I found during testing that as little as 120mA of current would draw the system down well below 26.3 volts and 160mA would draw it down below 20 volts, where it can't possibly work correctly.  I just reconfirmed this and a 160mA load draws the +30V supply down to just below 20 volts and the meter is severely inaccurate on a 20V input, reading less than 16 volts.  However, with the +30V supply loaded like this it will still pass a self test (!) and the TP301/TP302/TP303 voltages all read as you state--provided there's no input.  So that's no guarantee that all is good.

I realize that everyone seems to want a 'drop in' replacement for the VFD, but I concluded a while back that it just isn't feasible.  Even if your LEDs just happen to not draw quite enough current to cause a gross reading error, you've still overloaded that section of the power supply, which may cause a burnout in the future.  Also, I just couldn't see deliberately causing a change from specification--and lots of noise-- in the regulated power supply to one of the most critical components in the meter.  I've attached 3 scope shots--just driving the VFD, driving just 3 LED segments (out of 8 ) and with a fixed 160mA load.

I've ordered a few of your units--if the LED array is good, it's probably worth it for that.  I see they are selling quickly!

[AHOL]

Dear forum users! First of all, I want to thank everyone who bought my display module.

I confirm that the problem with the drop of + 30V is present in my module.

There is an exit.

I previously made a prototype with  duable-key control and power supply from the VFD filament Voltage, but refused it, since the filament winding does not provide enough LED current,
and I did not want to supply two wires from a +5V multimeter, BUT THIS CANNOT be AVOIDED.










The problem did not appear to me since I used CCR NSI50010YT1G. When using it, the drop is about 1.5V, but the voltage is still unstable.

The module can still be used in other applications according to the stated specification, BUT NOT IN THE FLUKE MULTIMETER.

Within 2-3 weeks I will make new boards with LED display, and I will send new boards in the quantity corresponding
to your current order to all buyers of the module for FREE.

I apologize for the inconvenience caused, this was not done intentionally.


Now a corrected module with additional + 5V power supply from a multimeter is now on sale.

[bdunham7]

Yes, the problem with a drop-in solution is that there just isn't enough current available anywhere.  Let me share how my setup works in case it helps you.  Mine requires some work to the main board, but is 100% electrically solid and provides plenty of LED current--my issue has been getting the display physically right.  If you have a good, bright display that fits, the other problems can be solved.

So the problem is translating the all-positive VFD control signals to a positive segment control and a ground-side digit control.  What I did is reuse the existing control circuitry and replaced the digit-grid driver, U215, with a ULN2803A darlington array.  This takes the same inputs as the original NE594s but instead of connecting the outputs to V_cc, it connects them to V_ss.  I then took U217 and U218 and changed their V_cc from the +30V regulated supply to the unregulated ~10.5V input to the 5V regulator--at the junction of CR601, CR602, C601 and VR601.  I just nipped the terminal with a flush cutter and soldered on a wire--truly pro!  This circuit can supply plenty of current and since I now have 10+ volts to work with, there's enough to handle the drops across the ULN2803A, the NE594, a CCD LED driver and two blue LEDs in series where needed.  So my board is just LEDs and CCD drivers.  I had to use 12 drivers, because although I could run two in series for the polarity sign, the '1' digit has both segments on the 'A' circuit and since I had common-cathode displays, I had to run them in parallel.

Since your board has the ground-side translator drivers on it, I think it could be adapted to work properly with just two bodges required.  First, the ground side would have to be disconnected from the VFD filament and run to the DIGITAL LO terminal.  Second, the segment-drive NE594s U217 and U218 would have to be bodged over to the 10V unregulated (or pre-regulated) supply.  I had thought of making a small board to go in place of U215/U217/U218 to make it look neater, but the bodge works well as-is.

If you wanted to stay as close as possible to drop-in, you could put 19 or 20 drivers on the board and just run two extra wires to ground and the power supply.  I wouldn't use the +5V regulated supply though, as tempting as it is to make it an easy plug-in installation.  I'm pretty sure most people wanting to replace their display on these can do a simple solder connection.

[AHOL]

Thanks for the answer.
Yes, I also thought about replacing the driver chip that is pin compatible but switches the outputs to ground instead of V+, but it is fiddles with soldering the drivers, which I wouldn't want to do.

And using + 5V (two wires) is probably the smallest change in the circuit;)

Drop on the + 5V bus when connected module only 20mV.

Usually you can receive signals from the processor and make an LED module with additional functions. I even bought a suitable display, but the price will be comparable to the price of a used multimeter.

Maybe I'll do it at my leisure;)

By the way, did you receive a letter via eBay?

[bdunham7]

I did get the message. I'll wait to see what you come up with in the meantime.  I'm also interested to see how bright the display is--i had to work pretty hard to get good viewing angles and acceptable levels of brightness after the front bezel is installed.  Is there any way your display LED could be made in a high-intensity red version?

I understand that a kit will sell better if less or no soldering is required.  I was looking for a good repair method, not a kit design.  I have no problems hacking away at the main board and even the bodge wires don't bother me much--they are ugly but solid.

Also, just an idea--if you are going to go from the +5V or the unregulated, you could bump the current up on the CCDs to 30 or even 40mA if you are using all on-board drivers.

[AHOL]

Can you email me on eBay?

This may not be the email address that eBay showed me.

The viewing angles and brightness are excellent, you'll see.
By the way, in my design the font was larger, but a factory that has been producing LEDs for many decades advised me to ensure that this type of font is displayed correctly on such a workspace. Both engineers and ergonomists do not recommend red as the primary color, only for signaling messages.

The LEDs used in the module have a current of 12-15mA and a supply voltage of 2.9V. This was my condition to reduce the problems of lack of power on some windings of the FLUKE transformer.

Most importantly, the low current of the LED ensures a long lifespan.

And you can do anything, including a red or red ERROR, there would be money;)

[YetAnotherTechie]

I previously made a prototype with  duable-key control and power supply from the VFD box winding, but refused it, since the filament winding does not provide enough LED current,

Just curious, but isn't the filament winding able to a watt or two?

[AHOL]

My module has LEDs with an operating current of 15mA and a supply voltage of 2.9V.
And even this is not provided by the filament winding.
The maximum that i managed to get is 4-5 mA.

After all, it is necessary to provide Ipulse=Icc*q^0,714

q - duty cycle 8

[up8051]

Can you share information where did you order custom LED?
I'm looking for manufacturer of custom 14-segment display.

[AHOL]

Any LED manufacturer will be able to fulfill your order.
The only advice I can give is to look for manufacturers in Hong Kong or China, they have a flexible pricing policy.

[AHOL]

Hello everybody!

Thanks to everyone who bought the display.
They sent everyone a replacement for a new (working) one.
Thank you for understanding!

Today I posted a new batch for sale on ebay. Link in the first post, there is also information on assembly.

On request, I add a schematic.

[strawberry]

unfair business practice https://youtu.be/Mt9jOJNHa88

[AHOL]

Thanks to all buyers!

Updated listing link (First post).
https://www.ebay.com/itm/154522071837

I draw your attention to the need to use anti static protection during assembly. Transistors are very sensitive to static voltage.

[bikeNomad]

I've also been working on a Fluke 8842A replacement display, and haven't yet got a diffuser that works well enough.

Going to an offshore supplier would require a MOQ.

AHOL, how many LED displays did you have to order?

I used the VFD supply pins connected to diodes, a 220µF capacitor, and a simple adjustable LM317 linear regulator (which lets me vary the brightness). I'm driving the LEDs with a 5V-capable microcontroller (with series resistors between the 30V logic inputs and the microcontroller digital input pins to limit input current). LED series resistance is provided by the ~50Ω microcontroller outputs. I did run a wire to digital ground.

I'm using 0603 white LEDs that have a forward voltage of 3.1V maximum (at 5mA).

I haven't looked at the effect on the various supply voltages yet, but it seems to work pretty well.

From my simulation, it looks like the 5V supply is providing about 100mA RMS through the transformer (for a load current of ~50mA).

A little switching supply would probably have been a better choice.

[AHOL]

Hi! I am glad to inform you that modules are on sale again.

https://www.ebay.com/itm/154545708329

[AHOL]

Let's raise for advertising.

[GigaJoe]

I have no clue about an original view of the bottom one , as it already was without the display, but here we are:
sense perception that bottom # a bit smaller, but not big deal. but letters def. are ; top one degrading , not even, but more less acceptable.

[philwong5176]

I am quite happy with the new display after using it for 2 weeks. The letters to the right of the digits are smaller than the original VFD but after a while it's not that bad.

If there's a Version 3 of the display I would recommend making the letters a bit bigger.

[AHOL]

I'm glad you liked it!

It was originally planned that the size of the letters will be the same as the original, but it had to be reduced, otherwise the adjacent characters will glow.
Magnification is possible, but it will be necessary to increase the displayed area, this is due to the technological process.
This will offset the display slightly from the original.

If colleagues support this idea, then you can try, by the way, you can make the ERROR symbol red.
How is this idea?

[batpuncher]

Recieved a couple, both working great.  Now I can try to find out why the 42 doesn't seem to power up.

[AHOL]

Dear colleagues, a new batch of modules.

Welcome: https://www.ebay.com/itm/154612343972

Best regards.

[Paceguy]

I'm glad you liked it!

It was originally planned that the size of the letters will be the same as the original, but it had to be reduced, otherwise the adjacent characters will glow.
Magnification is possible, but it will be necessary to increase the displayed area, this is due to the technological process.
This will offset the display slightly from the original.

If colleagues support this idea, then you can try, by the way, you can make the ERROR symbol red.
How is this idea?

Could there be a way to mask off the sides of the LED's to eliminate the glow effect on adjacent LED's inorder to accommodate larger letters?

[AHOL]

For clarity, I will show the difference in the displayed area, when changing the height of the letters





I have not made accurate measurements yet, this is an example.

But the creation of a module with enlarged letters is possible only after the completion of this project, since it requires financial costs.

[xwarp]

DO WANT!!!!!!!!!!

[Zucca]

This module uses a custom-made, industrially produced 7-segment display

Can you give me more information about how to produce/get such a custom LED display? Who is your supplier?

[AHOL]

Dave described how to design a custom multiplexed LCD display. https://www.eevblog.com/forum/blog/eevblog-1055-how-to-design-a-custom-lcd/

The LED display design is no different, even a little simpler.

According to your prepared drawings, any display manufacturer with more than 5 years of experience can handle the production of a display.

[AHOL]

Hello all,

Thanks to everyone who purchased the modules.
A new batch of modules will be ready for the New Year.
Unfortunately, COVID-19 is making its own adjustments.

I'll let you know.

P.S. If you wish, share a photo of the repairs made.

[bikeNomad]

I just installed one of the v4 displays in an 8840A which turned out to be broken. So I may decide to de-solder it.
But the display looks great.
Here's a comparison: the meter on the top has the LED display replacement, the meter on the bottom has a nice bright VFD display, and the meter in the middle has a somewhat dimmer display.

[BU508A]

Very cool! Thank you! 
I'm a bit late to the party so I'll wait for the new batch. 

[Cubdriver]

Very impressive!  Nicely done.

-Pat

[Kjo]

I can attest that the 2nd gen versions work just fine, albeit with annunciations that are a bit too small. I hope 3rd gen displays are better in this regard.

While one should be concerned about loading the +30V supply, it is quite tolerant of modest level conversion loading without impacting A/D performance. See the following thread I created on a universal OLED replacement display.
https://www.eevblog.com/forum/testgear/fluke-884042-series-universal-replacement-display/msg3862550/#msg3862550

I have used both active and passive 30:5V level converters to drive the OLED controller. The loading on the +30V supply varies from 500ua to 1.5ma per signal (8 grids, 11 segments), depending on the translator choice, and the main PCA passes all self tests. Of course this design cannot compete on cost with the blue LED replacement. There is just too much circuitry and assembly to do that.

On another note, one should be cautious in assuming that a blue LED replacement offers an inherently higher reliability or longevity than the original VFD. While I have LED based equipment from the 80’s that works flawlessly, this photo shows my 5year old Frigidaire LED display. It is rather obvious that modern LED devices are not flawless.


AHOL has not yet provided us with much manufacturing information, let alone reliability and longevity data. I don’t expect his volume is adequate for that anyhow. Still, it has brought back from the dead 4 of my Fluke 884X meters! For that I am thankful.

Kjo - KO3Y

[bdunham7]

While one should be concerned about loading the +30V supply, it is quite tolerant of modest level conversion loading without impacting A/D performance.

It is regulated, so as long as it doesn't get loaded down below the regulated voltage all is well.  After all the VFD current loads it in the original design.  Have you measured the 30V supply with your design?

[Kjo]

I can’t measure a significant difference either DC or on a scope from the OLED, blue LED or VFD for that matter. I can sometimes lock on 20-40mv synchronous noise, but can’t match it to anything. Also, I have never found any information on the VFD grid and segment currents, so there is nothing to compare to.

[bdunham7]

I can’t measure a significant difference either DC or on a scope from the OLED, blue LED or VFD for that matter. I can sometimes lock on 20-40mv synchronous noise, but can’t match it to anything. Also, I have never found any information on the VFD grid and segment currents, so there is nothing to compare to.

If it isn't sagging noticeably it should be fine.  I measured the VFD currents when I was working on my now abandoned display project and IIRC it was low single digit mA for the segments.  Never thought to measure the grids.

[Kjo]

Just for a reference, here are 2 OLED pics. Digital power is from the 5VDC lug and digital ground lug. There is no modification to the Fluke main PCA. The OLED controller is on the back of the VFD PCB. The 2 16 pin flat cables plug into the controller as they did to the VFD PCB.




Because a microcontroller is used, there are 7 selectable display modes plus a display demo mode.

Kjo - KO3Y

[AHOL]

Great job.
Yes, OLED looks modern. In the beginning, I also went down the path of creating such a display,



I even bought a suitable display, but gave it up for several reasons:
1) Lack of a display that exactly matches the dimensions of the VFD being replaced.
2) The high price of a ready-made module.
3) Relative unreliability due to the large number of components.

But in general, such a replacement is possible subject to a number of conditions:
- Lack of additional termal and electrical instability.
- Do not obstruct the installation of the AC board.

What I mean. Placing the display controller board in close proximity to thin film resistors can cause additional termal instability.
Unsurprisingly, FLUKE shielded the Z101 resistor circuit, which is located next to the A/D ASIC.



It seems to me that this should be taken into account.
In general, the display has the right to live without distorting the operation of the multimeter.

[Peteg]

Thanks for sharing, looks great.

[Kjo]

I can’t measure a significant difference either DC or on a scope from the OLED, blue LED or VFD for that matter. I can sometimes lock on 20-40mv synchronous noise, but can’t match it to anything. Also, I have never found any information on the VFD grid and segment currents, so there is nothing to compare to.

If it isn't sagging noticeably it should be fine.  I measured the VFD currents when I was working on my now abandoned display project and IIRC it was low single digit mA for the segments.  Never thought to measure the grids.

Good reference point for the segments. The translation device I used also draws ~1.4ma from a high segment line (and the same for grids but that is always 1:8 ). The VFD grids are driven to 30v so I would expect similar or higher given the size.

[AHOL]

Glad to meet everyone in the New Year!
All the best for the New Year!

A new batch of LED displays are on sale.

Listing link updated (first post).
https://www.ebay.com/itm/154780459035

[BU508A]

Ordered one. Thank you! 

[jonpaul]

Hello very fine work: Does the kit include step by step instructions or one muse go thru this very long thread to extract the procedure?



I have never disassembled the 8842A. Approx Time  to do the entire process,  1 hr? 1 day?

I will buy IF  if the procedure is easy and obvious but no time in my life to use up a day.

Many thanks

Jon

[Kjo]

I have replaced 3 VFDs with these LED units. You need to follow the service manual to disassemble the meter and extract
the VFD PCB. It is easily done but not trivial. Care must be taken to not damage any of the hybrid modules on the
main board. Dont take short cuts. You must have the basic skills to de-solder the VFD also. The traces are easily
damaged with too much heat.

Installation of the replacement to the PCB is easy. Reassembly is the reverse of disassembly.
Not a 1hr job.

[ErwinsCat]

Hi, is this kit still available to buyers? the eBay link seems broken.

[AHOL]

Hi, I am glad to announce that the display module is back in stock.

https://www.ebay.com/itm/154821741995

The delay was due to the exhaustion of the eBay selling limit for a month.

Regards, AHOL

[Teichhermelin]

I would also like to buy some...is there another source?

[AHOL]

Hi Teichhermelin, thank you for your interest!

The fact is that my current rating on ebay does not allow me to sell more than 10 pcs. per month.
The automatic request to increase the limit he tells me to take a hike...
I wrote an application for an increase in the limit, if they agree, I will soon put up a new batch, if not, then only in early March I will be able to continue selling.

In any case, I will report it here.

P.S.
If colleagues who bought leave their feedback on ebay, it will help to increase the rating and increase the limits.

Best wishes

[edavid]

Hi Teichhermelin, thank you for your interest!

The fact is that my current rating on ebay does not allow me to sell more than 10 pcs. per month.

Have you considered using tindie.com ?

[AHOL]

Have you considered using tindie.com ?

No, I didn't know about it, I'll look into it.
Thanks for the tip.

[jhunacek]

This looks awesome!  I would love to buy one if you find a way to sell them.

[PaulAm]

An 8840a is in my want list, so I grabbed one of these modules.  Looks really nice!

[Kjo]

Anyone heard from our Ukrainian LED display maker AHOL?

[giosif]

No and I hope he's ok.

[Mandokahn]

Hi folks,
I had a short conversation with AHOL via the ebay contact beginning April and in fact he told me that he hopes to resume his activities after the war (victory of ukraine).

This is what I hope as well!!

[tfrobase@gmail.com]

Will these be available anymore?  Looking for three sets ... thanks

[AHOL]

Hi all! I'm trying to restart production. The price has increased slightly due to logistics costs.
Here is a link to the listing:
https://www.ebay.com/itm/155146781718

P.S. Thanks to EVERYONE who expressed and expresses support and offers to help.

[wraper]

I suggest selling it with connectors crimped on wires. Not everyone who needs this has a proper tool to crimp.

[BigBoss]

If you work on the display issue of Fluke 45, I believe you'll find many customers including me .
It shouldn't be very difficult for you.. Right ?
I suggest you change the font and font size in next time. The fonts are a bit small in existing case.

[AHOL]

I suggest selling it with connectors crimped on wires. Not everyone who needs this has a proper tool to crimp.

The idea is not bad, but I think you can crimp two wires neatly even with pliers or solder. I will think about your offer.

[AHOL]

If you work on the display issue of Fluke 45, I believe you'll find many customers including me .
It shouldn't be very difficult for you.. Right ?
I suggest you change the font and font size in next time. The fonts are a bit small in existing case.

Above, I described that changing fonts will change the display geometry. So it is similar in size (only the font is a little smaller) to the original, when you change the fonts it will look completely different and I don’t know if users will like it or not.

[wraper]

The idea is not bad, but I think you can crimp two wires neatly even with pliers or solder. I will think about your offer.

Pliers is a very bad idea. Reliability will be atrocious and wire can be pulled out with a little bit of force.

[AHOL]

So I say that additionally solder.

[Mandokahn]

Hello AHOL, I received your display today and already replaced the old one.
The desoldering of the old one was tricky as the copper lines of the base board are very sensitive.
But at the end everyting works perfect.
It took me about 2 hours.
Thank you very much!!

[artag]

I would very happily buy something similar to this made to suit the HP53131A and similar counters.

[AHOL]

I would very happily buy something similar to this made to suit the HP53131A and similar counters.

Thanks for your interest in the module.
The fact is that the production of any module is associated with rather high costs. It cannot be produced in single copies. Capital investments amount to several thousand dollars.
There were many proposals for various modules. Unfortunately, this is currently not possible. Perhaps in the future, after the payback of this project, I will think about creating other modules.
Regards.

[staticresident]

+1 for another display

Crimped connectors would be nice, but not an absolute necessity.  Just make sure to add extra length so if people(me) fail the first time, they can cut the wire shorter and try again.

I have an 8842 on the way from ebay.  I have no idea what the display looks like, but I'll buy one of yours anyway just to have for the future. 

Price is a tricky issue for sellers, but I would not mind paying more for custom parts that keep a great meter alive.


I wish you and your country the best

[AHOL]

Hello!
It was possible to make a small batch of modules.
So please go to the store: https://www.ebay.com/itm/155392809126

P.S. Thanks to everyone who expressed and expresses support.

[tsirvoulis]

i just place an order
thank you

best regards from Greece.

Petros

[AHOL]

i just place an order
thank you

best regards from Greece.

Petros

Many thanks!
Will send it tomorrow.

[Crambone]

Just ordered one like the blue better, I always hated green.

[AHOL]

Thank you for the order.
To be precise, they are with a wavelength of 480-485 nm.
Close to cyan.

[AHOL]

I am updated the listing.
Welcome: https://www.ebay.com/itm/155392809126

[staticresident]

Another order in!  They are going fast. 

Thank you for hanging in there to make more. 

[AHOL]

Hi to all. A few more modules.
Welcome: https://www.ebay.com/itm/155422029090

[TomWinTejas]

Many thanks to AHOL for bringing this to market, it is a dramatic improvement and well worth the money and effort.  I am as newbie as one can get and was able to do the swap without damaging my 8842A.  I'll share my notes for any other total newbies, most of you can ignore what's likely obvious advice.

The disassembly guide in the owners manual was quite good.  I was nervous removing the switch extension rods because I was afraid to break anything plastic, but the switch parts were all quite sturdy.  When putting the extension rods back in place I did support them from under where I was applying pressure so there would be less pressure and that worked nicely.  I did manage to break one of the clips on the front panel where the screen board attaches to the metal frame.  I was able to use superglue to fix it, but with all of the pressure that didn't hold up.  But in the end it didn't matter as once the board is screwed into the front bezel everything is held in place (whew!). 

I didn't have a crimper for the included crimp ends and wound up using my precision needlenode pliers to do the crimp.  I tried pulling it off with a lot of force to test it and it didn't budge... so it was good enough.  I did find that for my 8842A the blades for 5V and GND were larger than the crimp end, so it was tricky getting them on... I had to use pliers to really push it down and even then I could only get them half way down. 

I was able to get away without removing the main board.  If you remove the plastic clips holding the board in place you can shift the board down enough to angle the screen board to remove and re-insert it.  I have the RMS AC module and did have to remove that. 

It was tricky desoldering the VFD, but I don't have much desoldering experience.  Even after it appeared to be desoldered there was enough solder in the thru-holes to bind the pins.  Liberal application of flux with the braid wasn't enough, nor was a solder sucker... but applying some fresh solder worked like a charm.  Others mentioned how fragile the pads are at high temperatures and perhaps I just got lucky, but with my Hakko 888D at 550F, I didn't have any problems.

[Crambone]

Installed mine the other day, very simple installation and looks great!

Thanks

[AHOL]

Hello all!
I am glad to announce that fresh modules are on sale.
Welcome.
https://www.ebay.com/itm/155514220604

[AHOL]

Attention buyers from regional eBay sites!!!

Shop online at ebay.com
The discount is valid only on .com, where everyone bought with a discount (from different countries).
This is probably due to the fact that regional sites are separate sites, and you need to create a separate listing there.

Happy shopping.

[AHOL]

Hi to all!
Thank you for shopping!
Another small batch of modules are on sale:
https://www.ebay.com/itm/155540541685

Welcome.

[Kjo]

For anyone looking for a quick turnaround on fully assembled Fluke display assemblies (#728873),
I now have them available using our new assemble PCB and the AHOL blue LED module. I am one of AHOLs
biggest customers, and no display repair on the Fluke 8840A/42A would be possible with out his development effort.

I have customers who just can't do the de-solder/solder rework reliably. I started by pre-wiring AHOLs modules.
But I always wanted a mechanical-only replacement. So I bit the bullet and re-engineered the Fluke display PCB
to work with both the AHOL blue LED module and our graphic OLED mono-color programmable display module.

Our module cannot compete with the AHOL display. But I hope that, with several avenues of repair, many more Fluke
8840A & 8842A meters will be saved from the scrap heap!


I have included a few pictures and links.

eBay
https://www.ebay.com/str/hollywoodcontrols/Suplus-Equipment/_i.html?store_cat=985206012

website
https://www.hollywoodcontrols.com/phpFluke/HC700013P.php

kjo KO3Y

[Kjo]

An update for this thread:

For anyone looking for a quick turnaround on fully assembled Fluke display assemblies (#728873),
I now have them available using our new assemble PCB and the AHOL blue LED module. I am one of AHOLs
biggest customers, and no display repair on the Fluke 8840A/42A would be possible with out his development effort.

I have customers who just can't do the de-solder/solder rework reliably. I started by pre-wiring AHOLs modules.
But I always wanted a mechanical-only replacement. So I bit the bullet and re-engineered the Fluke display PCB
to work with both the AHOL blue LED module and our graphic OLED mono-color programmable display module.

Our module cannot compete with the AHOL display. But I hope that, with several avenues of repair, many more Fluke
8840A & 8842A meters will be saved from the scrap heap!

The Fluke disassembly procedure should be followed. Dont try to shortcut.
Disconnect everything from the front panel including 2 16 pin ribbon cables.
Remove power bottom switch arms and F/R sw arm and cal sw arm.
Remove bottom shield. 
Remove 4 front panel screws.
Release ALL 6 main PCB rivets without breaking them.
Release main PCB below frame about 1.5".
Remove face plate.
release 2 plastic clip retainers from metal frame.
Remove display assy from frame. This is challenging.

Insert new assy as old one came out. The fit is tight, but it will go in!
Once in place, reverse everything and inspect before hooking up 5V display power!

You did unplug the meter from the mains....
You did use a static guard on your wrist...




I have included a few pictures and links.

eBay
https://www.ebay.com/str/hollywoodcontrols/Suplus-Equipment/_i.html?store_cat=985206012

website
https://www.hollywoodcontrols.com/phpFluke/Fluke_LED_Display.php
kjo KO3Y

[AHOL]

Hi to all!
Thank you for shopping!
Another small batch of modules for sale:
https://www.ebay.com/itm/155681025627

Welcome.

[AHOL]

Hi to all!
Thank you for shopping!
We continue to rebuild our FLUKEs

New small batch here:

https://www.ebay.com/itm/155853129116

Welcome.

[coromonadalix]

Nice to see some extra life given to theses meters ... 

aging vfd's  is a nightmare on many brands ...

[watchmaker]

Hi to all!
Thank you for shopping!
We continue to rebuild our FLUKEs

New small batch here:

https://www.ebay.com/itm/155853129116

Welcome.

I installed two of these.  Both from eBay.  One that was pretty much assembled, the other from Ukraine where you solder the header pins.  Both are easy, all the time is in getting to the display.  $80 USD vs $40 USD.  The boxes were exactly the same.

Both meters look identical as far as the displays go.

I can recommend either.  Its like everything else, the parts are cheap compared to the installation.

[AHOL]

Hi to all!
Thank you for shopping!
We continue to rebuild our FLUKEs

New small batch here:

https://www.ebay.com/itm/155853129116

Welcome.

I installed two of these.  Both from eBay.  One that was pretty much assembled, the other from Ukraine where you solder the header pins.  Both are easy, all the time is in getting to the display.  $80 USD vs $40 USD.  The boxes were exactly the same.

Both meters look identical as far as the displays go.

I can recommend either.  Its like everything else, the parts are cheap compared to the installation.

I am the developer and sole producer of this module.
All other solutions on the market use the module purchased from me.
I only sell on eBay under a nickname:
grudn_2015

My shop on eBay:
https://www.ebay.com/str/aholstore

The price at which I sell the module (without shipping and taxes): - $34.4

The set is sold only in the form shown in the photo:

[Paceguy]

I bought mine from AHOL who's located in Ukraine and the originator of these displays. There are other ebay sellers who are profiting from his work and selling them at a higher price. I was very pleased with AHOL's professionalism and fast service considering the conditions he and his fellow countrymen are living through. I suggest that one buys them from AHOL.

[watchmaker]

Please do consider the Fluke 45 display.  I do not care about fonts; and I suspect others agree.  My display is just a little dim, and I would not attempt rejuvenating it unless there is no other option.

Regards,

Dewey

[AHOL]

Please do consider the Fluke 45 display.  I do not care about fonts; and I suspect others agree.  My display is just a little dim, and I would not attempt rejuvenating it unless there is no other option.

Regards,

Dewey

Thanks for the suggestion, maybe I'll try something later. Now is not the best time for new projects.

[enut11]

Thank you @AHOL. I received my display kit 3 weeks earlier than forecast!
The only problem was that we were about to go on holidays 
Back now and looking forward to getting my 8842 back in service.
enut11

PS
5 stars for customer service

[enut11]

Just finished installing @AHOL's LED display in my Fluke 8842A DMM. Mostly went well and the effort was well worth it as the display is now brilliant. I purchased the basic kit so had to remove the old display from the Fluke PCB and install the new one.

Notes on my experience:
1) Follow the Fluke dis-assembly and re-assembly instructions in the manual step by step otherwise you can run into problems.
2) I removed the old display from the front PCB by pressing the glass back and forward until all the pins broke. I then de-soldered and removed the individual pins one at a time.
3) Cleaning up the holes on the Fluke PCB is important for proper fitting of the new display. My less-than-perfect cleanup meant that I had a small problem soldering the new pin headers.

On note 3) above, I suggest using longer header pins. In the photo below the kit header pins are at the top. The bottom set is about 4mm longer and this would have made a difference because the original pins barely went through the Fluke PCB.

All in all, a great upgrade for an 8842A with a dim or blank display.

Thanks a lot @AHOL

enut11

[AHOL]

Thank you @AHOL. I received my display kit 3 weeks earlier than forecast!
The only problem was that we were about to go on holidays 
Back now and looking forward to getting my 8842 back in service.
enut11

PS
5 stars for customer service

Thank you for the kind words!

I believe that these words should be addressed more to the employees of our post office, who risk their lives every day, delivering parcels.

[AHOL]

Just finished installing @AHOL's LED display in my Fluke 8842A DMM. Mostly went well and the effort was well worth it as the display is now brilliant. I purchased the basic kit so had to remove the old display from the Fluke PCB and install the new one.

Notes on my experience:
1) Follow the Fluke dis-assembly and re-assembly instructions in the manual step by step otherwise you can run into problems.
2) I removed the old display from the front PCB by pressing the glass back and forward until all the pins broke. I then de-soldered and removed the individual pins one at a time.
3) Cleaning up the holes on the Fluke PCB is important for proper fitting of the new display. My less-than-perfect cleanup meant that I had a small problem soldering the new pin headers.

On note 3) above, I suggest using longer header pins. In the photo below the kit header pins are at the top. The bottom set is about 4mm longer and this would have made a difference because the original pins barely went through the Fluke PCB.

All in all, a great upgrade for an 8842A with a dim or blank display.

Thanks a lot @AHOL

enut11

For soldering, I use a gel-like flux with good immersion and a high intensity of the effect of penetration into the seams. High wetting, high strength of connections.

[AHOL]

Thanks to everyone who bought my module. Happy and accurate measurements to you!

We continue to bring the wonderful FLUKE 8840/42A multimeter back to life.
New batch of modules here:

https://www.ebay.com/itm/156079740588

Best regards,
AHOL