Fluke 45, replace dead VFD by 7-14 segment LED display´s

[Satbeginner]

Hi all,

I bought a Fluke 45 on eBay, "Not Working", "As Is", " For Parts", so when it arrived it did not work, this was not a problem.

But my goal is to repair this meter, and since I already had a Fluke 45, finding the problem was fairly easy: the VFD (Display) is broken.
By exchanging the two displays I  could confirm the meter is still working, just not showing anything.

Are there members that recently were able to buy Fluke spareparts?
And if so, where?

I live in Spain, but have family in The Netherlands, so I am flexible in terms of location.

It is this part (just the display) that I need.

Un saludo,

Satbeginner

[Ian.M]

Explain 'broken'.  Is the VFD glass physically damaged?  The filaments look to be intact - is that the bad display or the good one?  Are the Getter spots on the left the same colour on the good and bad displays?  If its lost vacuum they've probably gone whitish, but if they are both still dark or metallic looking odds are its still got vacuum.  If the filaments and the getter spots are good, odds are its a problem with its supply voltages or the driver chip.

[Satbeginner]

It´s really broken, the little tube on the top left corner used during manufacturing to suck the vacuum, broke off.

So inside mechanically it is still OK, but instead of a VFD it is now an AFD (Air Filled Display).....

[SeanB]

Rest of the board still likely works, so all you need is the actual VFD and solder it to the board.

[Ian.M]

Unfortunately it looks like Fluke 45 spares were put on 'Last Time Buy' back in 2009 so you are probably S.O.L. unless you can get another parts meter, or can find one N.O.S. at whatever boutique price is being asked, or want to take on the considerable challenge of reverse engineering the display board and designing an compatible replacement using a graphic matrix display that emulates the VFD + controller.

Its probably worth asking here if anyone's replaced a dim display and still has the old one available - if the filament voltage can be boosted a bit you'd probably be able to get the emission up enough to get a few more years life out of it.

[Satbeginner]

Hi Ian and others,

I am afraid you´re right, finding a ´new / replacement´ display is the only way for me.
I do know the rest IS working, because I have another 45, and I switched display´s, and everything seems to work.

So, my humble question you you all is: 

Is there anybody with a dim Fluke 45 display floating around, or maybe a 45 that was struck by a direct hit from lightning?? (pretty sure the display has survived  )

Thanks to you all for the help offered,

Un saludo,

Satbeginner

[Satbeginner]

Hi @Ian.M , #Ian.M ,

redesigning a display board would be a challenge because of the serial in- and output it uses, but you gave me an idea: Maybe no redesign is needed??

I could re-use the existing board, because a VFD has all the individual digits, +/- signs and comma-dots wired to it´s outside pins.
So I should be able to do some current limiting and level shifting and be able to drive a common anode or cathode (instead of the VFD-grid, have to look into this) 7-segment LED display for the numbers, and some LED´s for the functions?

I have seen that my board (my meter is from 1985) uses a different VFD driver chip than the one in the servicemanual.
The manual uses a 75212, I have an D7527ACU, but they seem to do the same thing, because all the signals from the main board to the displayboard are identical.

I´ll try to do some basic testing on this.

Un saludo,

Satbeginner

[Satbeginner]

replacing the Fluke 45 VFD by 7 (and 14) segment LED display can be done, here is the "proof of concept".

In my Fluke 45 with the dead VFD (Vacuum gone) Fluke used a D7527 VFD display controller.
In my copy of the service manual the use something else, but I think they are functionally compatible.

An individual segment of a VFD lights up when both Grid (digit) and Anode (segment) are at +5V, this is positive to the filament AC level.
When a VFD segment is not used, both Grid and Anode are at a negative level.

In real life, these signals move between -32V and +5V.

According to the datasheet of the D7527 all outputs are capable of delivering up to 30mA.
Based on this, I "fiddled" the following solution, where I use about 6mA per LED segment.

I use the diodes (1N4148) to remove the negative -32V, now only using the +5V part of the signal,  followed by a NPN switch transistor to drive the Common Cathode Digit´s.

The LED current is supplied by the VFD-driver chip, again, negative voltages are removed by the serial diodes, current limiting is done by the 470 Ohm resistors. (appr. 6mA)

The reason I remove the Negative voltages, is to protect the display LED´s against reverse breakdown.

I found the five "number" digits can be a combined display who share the segment wires, the minus-sign has to be a separate digit, because segment wire 10 is used for the minus-sign, but it shares the same digit wire as the MSD.

I have not yet tried the second display.

un saludo,

Satbeginner

[carl_lab]

Well done! 

[rsjsouza]

Satbeginner, thank you for sharing your investigation. I love these modifications!

[Ian.M]

Looks like you are getting somewhere.   Time to start designing a PCB and selecting parts.   If you use SMD 7 segment LEDs, you may even be able to come up with a daughterboard that effectively replaces the VFD with only a single flying jumper for Gnd.  That's a marketable product . . . .

[Satbeginner]

Hi Ian.M,

there is physical space available to make a "thin" pcb that would fit in place of the original VFD.
I am looking for parts right now, but I have a few concerns:

- Thickness, probably do-able with SMD displays;
- The huge amount of extra indicators, like AC, DC, Hz, (m)A, V, dB, etc. (Thinking of using LED bars with a silk-screen in front)

My first  test will be something like 2x a normal 5digit common cathode 0.36" display, with a separate digit in front of this for the minus-sign.

I had a look at how to do the secondary display: In the original VFD they use something like a (but not really) 14-segment display in three digit´s, but I could not find any application for these extra segments, so I just think of leaving them out. (I´ll use 7-segments, so, just numbers there, and simple characters like ´print´)

Keep you posted about any progress,

Un saludo,

Satbeginner (Leo)

[netdudeuk]

Good work.

Here's another example of a forum member overcoming the issue of a broken display on an old instrument -

https://youtu.be/H9_Jwy-2vXU

[Johnny10]

Hey,
You've got way too much time on your hands!

 

[bitseeker]

Satbeginner,

I like where you're going with this and how you adapted the existing drivers. The LEDs should look great when you have it all running. Looking forward to seeing how it turns out. If you do end up making replacement modules or kits, I wonder what will happen to the price of 45's on eBay.

[lowimpedance]

 Replacing the VFD is quite doable and your off to a good start. Keep going it will be most interesting to see the final result.

Satbeginner,

I like where you're going with this and how you adapted the existing drivers. The LEDs should look great when you have it all running. Looking forward to seeing how it turns out. If you do end up making replacement modules or kits, I wonder what will happen to the price of 45's on eBay.

Does the 45 VFD fair worse than similar vintage DMMs , ie 8840, or is the 45 more useful than the rather basic 8840 function wise ?.

I had a go some time ago with an 8840a that had very much seen better days ! . Had some rough treatment resulting in a broken display etc.
Only persevered with it as a learning experience, (and that I knew that it worked apart from the display).
 Had to come up with a suitable way to display the annunciators so I used a led behind a film printed reversed with the function clear.
The 8840 uses multiplexing, not sure what the 45 does, but I had quite some difficulty with 'ghosting' of LED's that were not supposed to be on.
A couple of pics of the display working. Note the display actually has better contrast better than the photo lets on. (except the MSD 1 which turned out to be brighter annoyingly even though I played with the average value of current through each LED, quite a pain with the multiplexing).
And yes I know its as ugly as a hat full  , but hey it works and was a "can it be done exercise" without huge effort anyway.

[bitseeker]

If you do end up making replacement modules or kits, I wonder what will happen to the price of 45's on eBay.

Does the 45 VFD fair worse than similar vintage DMMs , ie 8840, or is the 45 more useful than the rather basic 8840 function wise ?.

I haven't noticed it doing necessarily better or worse (nor have I kept meticulous records), but if there's an easy kit or module to revive the aging meter, people may be willing to invest a bit more in their bidding. Just speculation.

The Fluke 45's dual display is a worthy trade-off for its lower (but still very useful) resolution.

I had a go some time ago with an 8840a that had very much seen better days ! . Had some rough treatment resulting in a broken display etc.
Only persevered with it as a learning experience, (and that I knew that it worked apart from the display).
...
And yes I know its as ugly as a hat full  , but hey it works and was a "can it be done exercise" without huge effort anyway.

That's quite a good, and working, proof of concept if you ask me.

[Satbeginner]

Hi all,

I already have a Fluke 45 in perfect working order, and I love it for repair/troubleshooting, because I see both DC-voltage AND ripple without the need of changing settings of the meter.

Call me crazy, but I bought the broken one, just because it was broken........ and I needed a WRP.
This is what I call a Winter Repair Project.

A WRP may not be all that useful, but it keeps me busy and off the streets, and I need a challenge every now and then.

I think of doing the same with the indicators: an LED bar with a laserprinted film showing the text in B/W reverse in front of that.

In parallel of this Fluke 45 exercise, I am repairing a HP 3457A as a WRP as well.
That one is doing measurements OK now, but the selftest is still giving an error 64, I give info on that in another thread.

un saludo,

Satbeginner (Leo)

[bitseeker]

Sounds great, Leo. Keep up the good work.

Being able to see ripple along with DC is exactly why I use a dual-display handheld DMM when checking power supplies. My bench supplies are just single display.

[Satbeginner]

Hi all,

parts are ordered at AliExpress, but due to the Chinese New Year, there is some delay in this little project.
Will keep all you posted.

Un saludo,

Satbeginner (Leo)

P.S. since my HP 3457A repair was successful, I do need something else to do.... 
https://www.eevblog.com/forum/repair/hp-3457a-multimeter-repair-advice-needed/

[bitseeker]

due to the Chinese New Year, there is some delay in this little project.
Will keep all you posted.

Yeah, funny how that works. I guess we can take some time off for Chinese New Year. 

[Satbeginner]

Hi all, back again.

There is progress, although I still need two "one digit" 7-segment displays to create the 'minus' sign. (temporarily done by using red LED's)

I used 2pcs blue 5-digit common cathode displays for the two measuring values, and 4pcs blue 10-bar indicators for the functional indicators.
I am going to mask these LED bars with a text display on transparent polyester film, but I need to get some sheets to be able to print this on a laserprinter.

Instead of the original VFD I placed some single row female connectors on the back of the Fluke display PCB.
The additional driver electronics (14x segment and 11x Digit) are placed on a piggy-back board that plugs in the original display board, two thin cable bundles run to the actual replacement LED-displays.
All the signals I needed are available on the VFD connctor-pins, I just had to add extra pins for ground.

The LED-displays are placed in a way they just fit inside the window in the cabinet, so they are flush with the colored Fluke window.
This just gave enough room for a display-print using normal components with the wires on the back between the original print and the front window.

I choose to do it 'breadboard-style' because I only wanted to repair this one meter, obviously a much nicer result could be obtained using SMD components and a real PCB, but from the outside it does look kinda cool.

Un saludo,

Satbeginner

Here some pictures:

P.S. the intensity difference has to do with the camera, not with the display.

[george.b]

but from the outside it does look kinda cool.

It looks great! Well done!

[Johnny10]

Bravo!

[bitseeker]

That looks fantastic! Bravo!

Using single rectangular LEDs for the negative sign will probably be fine. They look round due to bleed. Just mask, using heat shrink tubing, electrical tape or black paint, the parts of the LED that should not show in order to get a sharp rectangle.

[james_s]

That really looks a lot better than I would have imagined. I don't think I'd have even noticed it wasn't original from the photo unless I looked really closely. I'm reminded that I have a Fluke 45 that I hardly ever use, I really must clean up the bench sometime and give it a more permanent home.

[lowimpedance]

Stirling job right down to the cable looming  .
Looks like there is a good amount of space to add the extra piggy back board on the 45.
 The 8840 does not have any more available space than the VFD so was quite a crush getting all the display and wiring in for my display mod.
I also used proto board too and as you say doing a PCB with SMD parts would have made it easier.
But for my 8840 the display bezel was beyond help as well so I had to rebuild that too anyway and thus the choice of red LEDs.
The blue LEDs and bar graph do look much nicer though.

[Cubdriver]

Wow - that's an amazing job - very nicely done!     I'm not familiar with that meter, so at a glance I thought the first picture with the lighted display was of the other, working meter you said that you have.

Look forward to seeing the finished product once you get the missing '-' symbols and the text mask over the indicator lights and button it up.

-Pat

[bitseeker]

It is amazing isn't it? The blue LEDs really give it the VFD look & feel.

[Cubdriver]

And how!

-Pat

[bitseeker]

Almost makes me want to add badly faded Fluke 45 meters to my shopping list. Oh, my aching TEA.

[james_s]

If you wanted to really go the extra mile, find some of those big flat faced rectangular LEDs and laser print masks on waterslide decal film. Apply that to the LEDs then paint the sides black to prevent light bleed and you'd get the nice alpha indications too.

[Satbeginner]

Hi all,

again some progress (baby steps): the (I choose Red for negative) single digit 7-segment displays arrived today, so I put those in.
The only thing I still have to do is find the A4 polyester film so I can print the "letter-mask" for the indicators.
(Difficult in a small Spanish pueblo....)

I managed to make the mask in "Word", using a monospaced font called 'Lucinda Console'.
It needed some playing around with the character size and spacing but using size 5 and spacing extended with 0,6 point gave me a 0,1" spacing like the LED-bars.
I also shrunk the line-spacing using 'exact 5 points', so I could use 3-chars terms like 'CAL', 'BAT', 'MIN', etc.

When I can print this on a transparent film in real black on my laserprinter it should work OK. (the picture is still paper)

Un saludo,

Satbeginner

[Satbeginner]

P.S.

although cool on the outside, it's only fair to show the inside too, in real life, having a compact display-board like this means a lot of wires!!

Un saludo,
Satbeginner (Leo)

[Richard Head]

Gosh I've just found an old Fluke 45 VFD in my junk box. Do you want it?

[bitseeker]

That's quite a bundle of wires all right. Next generation goes to PCB.

[james_s]

Well if you can find a few people who need one, there might be a market for a nicely done PCB. In the meantime just keep the cover on and nobody will ever know. It's sort of like software, if it looks good on the outside nobody has to know your code is a mess, at least that seems to be how it works.

[Satbeginner]

Gosh I've just found an old Fluke 45 VFD in my junk box. Do you want it?

Hi, I would like to have it, because I have a second 45, so you never know.   

Can you send me a pm please with the cost and shipping?

Un saludo,

Satbeginner (Leo)

[Richard Head]

Satbeginner I'm pulling your leg! After all that good work I thought that you'd tear your hair out if you managed to get one in the end.
Actually I do have one but it's in my (working) Fluke 45.
Nice job and don't be too angry with me.

[Satbeginner]

No worries, I already thought it was to good to be true.

And now I can say I have (probably the only one in the world...) a Fluke 45 with a color display. :-)

I love a practical joke!!

Un saludo,

Satbeginner (Leo)

[Dtec]

I'll give you a fluke 8840a with bad vfd for the board to replace another 8840 a also own a fluke 45 dual display will pay for that board pm me with price


Sent from my iPad using Tapatalk

[Satbeginner]

I'll give you a fluke 8840a with bad vfd for the board to replace another 8840 a also own a fluke 45 dual display will pay for that board pm me with price

Hi Dtec,

I am afraid I do not completely understand your question/offer:

I do not have a board for sale, I also did not make a special PCB for the display repair, I just did a "one time off" breadboard project to revive my Fluke 45.
The simple schematics I used are in the beginning of this thread, anybody who want can use these.

I re-used the VFD display driver chip, and put some simple components in between so it could drive the LED's with several mA's.

Very soon I will post pictures of the final result, I am still waiting for the laserprintable polyester foil.

Un saludo,

Satbeginner (Leo)

[bitseeker]

Congrats, Leo, on your first product request. The confusion is understandable given the fantastic results you achieved.

I went back to the beginning of the thread and scanned the posts on the first page, but didn't see the schematic you referred to.

[Satbeginner]

Congrats, Leo, on your first product request. The confusion is understandable given the fantastic results you achieved.

I went back to the beginning of the thread and scanned the posts on the first page, but didn't see the schematic you referred to.

I posted the basic "schema" being just a transistor driver per digit, and a current limiting resistor per segment.... :-)
To be clear, I used the VFD driver chip, I just replaced the VFD by a basic driver circuit and 7-segment LED displays.

For both the numeric displays I used a 5-digit display with shared segment pins.
The minus signs needed to be separated, because the share indicators as well.
For the indicators -like AC, DC, m, V, Ohm, etc.- I used LED "volume-type" bar arrays. (they have their own current limiting resistor as well)

Un saludo,

Satbeginner

[bitseeker]

Ah, OK. Got it. Thanks, Leo!

[Satbeginner]

Today I (finally...) received the polyester film for my laserprinter, so I could print a "display mask".

I am not happy yet, because the black around the indicators (m, V, AC, etc.) is not black enough, but it "sort of" works.

Un saludo,

Satbeginner (Leo)

[bitseeker]

Yeah, it's going to be hard to block all the light with a thin layer of toner. What if you use two masks to double the density of the toner? Does it create any side effects (diffusion, fringing, etc.)?

[Satbeginner]

Yeah, it's going to be hard to block all the light with a thin layer of toner. What if you use two masks to double the density of the toner? Does it create any side effects (diffusion, fringing, etc.)?

Will try that this weekend by printing the same mask 3 or 4 times on the same sheet, and then cut them all and put them together, so I'll have multiple layers.

Keep you posted.

[james_s]

You could get a really nice result if you can find someone to plot it on photographic film. Especially something like xray film that has an emulsion on both sides. You can get really nice solid black with film.

[eliocor]

You can prepare a .PDF and go to printing service shop: they can print your file on film which have a very high density and resolution (not less than 2400DPI).
When I need to make some (homemade) PCB prototypes with very small geometry (5-6 mils) I prefer to use such service: the cost is about 10€ for an A4 film (but only 22€ for an A2+) and the results are optimal!

[rsjsouza]

Today I (finally...) received the polyester film for my laserprinter, so I could print a "display mask".

I am not happy yet, because the black around the indicators (m, V, AC, etc.) is not black enough, but it "sort of" works.

Yes, as others have said, toner is not the best if you need to completely block light.

I still remember when I tried to make a PCB and used my laser printer to create the photomask...  What I did at the time was go to a shop that did silk-screen and they printed my stuff in photographic film (or it was a simple transparency - I can't recall).

[nidlaX]

Hey, check out what just showed up on eBay!
http://www.ebay.com/itm/Fluke-45-Multimeter-Non-Working-for-parts-/112422725263

Seems like somebody's got some ideas for your photos Leo.

[Satbeginner]

Well , well, well, he's a bit cheeky, isn't he??

His bad, there is probably only ONE Fluke 45 in the whole world having a blue LED Display, and he choose these pictures to use......

But this is eBay, this seller is "selling" something that he definitely does not have, so an unfortunate buyer will receive something very different.....
Maybe somebody can ask him for the SN?? Then I can post mine here too, just for fun??

[nidlaX]

Well , well, well, he's a bit cheeky, isn't he??

His bad, there is probably only ONE Fluke 45 in the whole world having a blue LED Display, and he choose these pictures to use......

But this is eBay, this seller is "selling" something that he definitely does not have, so an unfortunate buyer will receive something very different.....
Maybe somebody can ask him for the SN?? Then I can post mine here too, just for fun??

He's added a picture of the actual unit. Not sure why he chose to use your picture in the first place.

[Satbeginner]

Well , well, well, he's a bit cheeky, isn't he??

His bad, there is probably only ONE Fluke 45 in the whole world having a blue LED Display, and he choose these pictures to use......

But this is eBay, this seller is "selling" something that he definitely does not have, so an unfortunate buyer will receive something very different.....
Maybe somebody can ask him for the SN?? Then I can post mine here too, just for fun??

He's added a picture of the actual unit. Not sure why he chose to use your picture in the first place.

We will never know if the "other pictures" are "the actual unit", won't we... 

[bitseeker]

Yeah, that's pretty strange. I messaged the seller to let him know that I know that photo isn't his. His reply was that he doesn't ship outside the US.

"Hello, McFly," I'm in the US.

So, I flagged his listing as potentially fraudulent. Maybe it'll help the high bidder if it ends up not being what he expected and contacts eBay.

[coromonadalix]

i have contacted him too may 29, ive told him the picture is not legit, and taken from this forum, i reported him on ebay ... fraudulent seller and Ebay did  nothing

he said : Sorry about the pic. I took some fresh ones of the item, but Ebay wont let me remove or replace the original listing pic. We will have to bear to the end of the auction I guess.

Sorry



pffffff

[PedroDaGr8]

OP can do a DMCA takedown request on the item. That will take care of the stolen image.

[coromonadalix]

The Ebay sell is still going on   loll  5 bids

[bitseeker]

he said : Sorry about the pic. I took some fresh ones of the item, but Ebay wont let me remove or replace the original listing pic. We will have to bear to the end of the auction I guess.

Pffft is right. What a liar.

The Ebay sell is still going on   loll  5 bids

Yeah, 4 of the 5 bids are from a zero-feedback buyer. We may never know what becomes of it.

[Cubdriver]

I wonder if that might be cause for a 'not as described' case when the meter arrives, as the stolen image purports to show it with all the segments lit, and we ALL know that it will not look at all like what is shown?  Interesting that HIS pics don't show it lit up...   

-Pat

[Ian.M]

http://pages.ebay.com/seller-center/listing/create-effective-listings/vero-program.html

Its still got two and a half days left to run so report it for use of your photo without permission.   Scum sellers like that need to be actively LARTed.

You may need Dave to confirm that  copyright in all media posted to the EEVblog forums remains with the original owner, but that can be dealt with later if EBAY query the report.   Proving ownership of the photo should be fairly easy - another photo of the modded and unmodded Fluke 45 meters side by side on the same test bench with today's headlines of a national paper in the shot, taken on the same camera + the original photo file should be enough to show you have current access to the equipment and location, and the equipment has been uniquely modded.

[bitseeker]

I wonder if that might be cause for a 'not as described' case when the meter arrives, as the stolen image purports to show it with all the segments lit, and we ALL know that it will not look at all like what is shown? 

I'm not sure since "For parts not working" condition does not benefit from eBay Buyer Protection. The spirit of the buyer protection should make this qualify, but it may come down to who you happen to get on the phone when you call in the complaint.

[Cubdriver]

I wonder if that might be cause for a 'not as described' case when the meter arrives, as the stolen image purports to show it with all the segments lit, and we ALL know that it will not look at all like what is shown? 

I'm not sure since "For parts not working" condition does not benefit from eBay Buyer Protection. The spirit of the buyer protection should make this qualify, but it may come down to who you happen to get on the phone when you call in the complaint.

Yeah, I'm not sure how that would work.  Using a stolen picture should certainly count as a big negative in my mind, but we all know that eBay moves in mysterious ways.

Someone got it for $62 plus shipping.  I hope they don't wind up too badly hosed.

-Pat

[bench_knob]

@LowImpedance,
Got any shots of the insides of your 8840? I recently bought an 8840A on eBay, --the seller misrepresented the display quality. The received DMM works well, but the display is almost unseeable in daylight hours. So, I've been thinking about replacing the VFD with LEDs. I did a quick DuckDuckGo (they don't track ya, & disable JS using NoScript) search on the 'Net & up popped your post here. Why reinvent when I can ask? As I understand things, 'ghosting' is purportedly caused by the capcitance between the Fluke VFD elements and which they resolved by incorporating an appropriate blanking period. But I suspect that there might also be a bit of phospher persistence at work as well. LEDs exhibit very fast on/off times, I introspected about that a bit. How did you resolve that matter. You cook up single-shot latch arrangement?   

In any case, your annuciator solution and placement is excellent, the whole remedy is quite good in my opinion. It looks great!
Thanks in advance
bench_knob

[Zucca]

suggestion for the next VFD broken adventure:

https://www.eevblog.com/forum/repair/hp-34401a-dmm-with-leaking-segments/msg1627666/#msg1627666