I had two Fluke 8010A Bench Meters both with broken LED displays (they go black). First time I looked at replacing the LCD with LED it looked impossible because the common BP (backplane) signal reverses phase constantly relative to the segment drive signals (that's what LCD displays need to work).
A few months later I had another look and realised that a pnp transistor could use the BP signal to strobe the right phase for four Common Cathode Seven Segment LED's by doing this:-
"Connect BP signal to base of PNP transistor via 3K9 resistor, Connect its emitter to all four LED common cathodes, connect its collector to - Vss
(Note BP drives U6 for the decimal points)"
Solder wires from the previously LCD connector to your four common cathode seven segment LED's. See attached pinouts etc. Only three of the LED decimal points need to be connected to U6.
The ICL7106 doesn't have much drive but its enough to get a tidy LED display, don't include any series resistors. The LED's take a bit more current so its a good idea to increase the power supply smoothing capacitors (double the uF value)
So end result is an excellent and accurate Fluke 8010A with four digit LED display (the MSD LED only displays "1" and the negative sign.
The Fluke 8010A has a very small supply transformer and only consumes a few watts. I have one of the 8010A's permanently on monitoring a battery voltage.
A few months later I had another look and realised that a pnp transistor could use the BP signal to strobe the right phase for four Common Cathode Seven Segment LED's by doing this:-
"Connect BP signal to base of PNP transistor via 3K9 resistor, Connect its emitter to all four LED common cathodes, connect its collector to - Vss
(Note BP drives U6 for the decimal points)"
Solder wires from the previously LCD connector to your four common cathode seven segment LED's. See attached pinouts etc. Only three of the LED decimal points need to be connected to U6.
The ICL7106 doesn't have much drive but its enough to get a tidy LED display, don't include any series resistors. The LED's take a bit more current so its a good idea to increase the power supply smoothing capacitors (double the uF value)
So end result is an excellent and accurate Fluke 8010A with four digit LED display (the MSD LED only displays "1" and the negative sign.
The Fluke 8010A has a very small supply transformer and only consumes a few watts. I have one of the 8010A's permanently on monitoring a battery voltage.
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Now we just need someone to do it for Fluke 8842s, since the VFDs have become nearly impossible to get. Eventually I might get around to doing it myself. We'll have to see.
Sometimes there's static dust covering on the fluro display, due to high voltage. A wipe down may help.
Many thanks.
The LED's I used were Red GaAlAs types, plenty bright enough. You reminded me about the leading "1" first attempt the leading "1" wasn't bright enough because one ICL7106 pin has to drive both segments B4 and C4.
I'm attaching a circuit diagram showing how leading "1" brightness was fixed.
Same conversion from LCD to LED can be done with the Fluke 8012A.
See attached.
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Converting the Fluke 8842A display digits to LED looks possible, the various indications would be more difficult mechanically.
Converting the Fluke 8842A display digits to LED has to be a last resort if the Fluorescent Display became obsolete/unobtainable.
Probably remove the three UDN6118A IC's U215, U217 and U218 and bridge the TTL signals across with resistors. The 74LS IC's will sink enough current to drive LED's. The signals coming directly from U212 should really go through an added 74LS IC. Add pull up resistors where needed.
Maybe use two modules of three LED's each for the six digits because the strobe signals G0 - G7 are provided.
Looks like the Fluke 8842A is too recent for such a conversion. I did the Fluke 8010A and 8050A meters I have because they work so well (even after 40 years) and I couldn't get new LCD's (and the LED's look smarter and are easier to read than LCD).
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richgwilliams - A big THANK YOU for your post - Easy to understand details on how to convert to the new 7 segment display.
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You are welcome, thanks for letting us know. Glad it helped to keep another 8010A going, one of the two 8010A Flukes I converted is always on, 24 hrs a day, connected to monitor solar power battery voltage.
Hey Rich,
Pardon a really stupid question ... buy why didn't you simply use a DVM module off AliExpress? They are cheap, small with minimal energy use. Using that Fluke is kind of overkill and LEDs do age.
Probably could have stuck the module to the side of the solar battery controller or batteries with double sided tape. lol!
Pardon a really stupid question ... buy why didn't you simply use a DVM module off AliExpress? They are cheap, small with minimal energy use. Using that Fluke is kind of overkill and LEDs do age.
Probably could have stuck the module to the side of the solar battery controller or batteries with double sided tape. lol!
Hi @anatech That's actually a good question. Logically I agree with you that a new LCD DVM module would have been fine. The sequence of events for me was as follows:-
1. I had a few old LCD Fluke bench DVM's and I wanted to get them working and I wanted to preserve them.
2. I had a lot of common cathode 7seg LED's but nowhere could I buy LCD's for the Flukes.
3. I modified four meters 2 x 8050A 1 x 8012A and the 8010A shown.
4. I needed to monitor the charge voltage of the solar battery, the Fluke 8010A is very low power, see photo of the line transformer below.
5. The LED display is clearly visible from a distance day and night.
6. I didn't have the idea of using a new LCD module.
In summary Fluke have an unequalled reputation for long life, accuracy, stability and durability so out of respect for Fluke I could not throw these old DVM's away.
The photo showing the very small line transformer and the LED connections:-
.
1. I had a few old LCD Fluke bench DVM's and I wanted to get them working and I wanted to preserve them.
2. I had a lot of common cathode 7seg LED's but nowhere could I buy LCD's for the Flukes.
3. I modified four meters 2 x 8050A 1 x 8012A and the 8010A shown.
4. I needed to monitor the charge voltage of the solar battery, the Fluke 8010A is very low power, see photo of the line transformer below.
5. The LED display is clearly visible from a distance day and night.
6. I didn't have the idea of using a new LCD module.
In summary Fluke have an unequalled reputation for long life, accuracy, stability and durability so out of respect for Fluke I could not throw these old DVM's away.
The photo showing the very small line transformer and the LED connections:-
.
Not sure about that, I have 7seg LED displays here that go back to the 1970's and they still work fine. In my experience LCD displays are sometimes unreliable after a long enough time.
Here is an old Commodore calculator from the 1970's and the tiny LED display still works fine!
Hi Rich,
I am in audio service, and test equipment repair and calibration. I have replaced many LED displays and the one in my ShibaSoku THD meter are dim and need replacement. Countless LED clock segments go dim. Proof isn't very hard to find if you look. LED displays take a lot of power to run.
LCD displays can go bad, especially if there is a net DC across the segment. They do not like that and some companies designed equipment this way. My HP LCD displays are still sharp and clear.
Fluorescent displays also dim over time depending on the brightness and run time.
I had some calculators with those magnified LED displays that went bad, normally open segment.
Anyway, a cheap voltmeter module probably costs less than the LED displays you bought for your meter. For your use, you can easily buy 4 1/2 digit meter assemblies if you want high accuracy. Tiny, cheap. A 3 1/2 digit model would suffice.
Just saying. I probably would have bought an LCD display with serial data in that fit the opening.
I am in audio service, and test equipment repair and calibration. I have replaced many LED displays and the one in my ShibaSoku THD meter are dim and need replacement. Countless LED clock segments go dim. Proof isn't very hard to find if you look. LED displays take a lot of power to run.
LCD displays can go bad, especially if there is a net DC across the segment. They do not like that and some companies designed equipment this way. My HP LCD displays are still sharp and clear.
Fluorescent displays also dim over time depending on the brightness and run time.
I had some calculators with those magnified LED displays that went bad, normally open segment.
Anyway, a cheap voltmeter module probably costs less than the LED displays you bought for your meter. For your use, you can easily buy 4 1/2 digit meter assemblies if you want high accuracy. Tiny, cheap. A 3 1/2 digit model would suffice.
Just saying. I probably would have bought an LCD display with serial data in that fit the opening.
Its an interesting comparison.
Have a look at the attached Vishay datasheet for a 13mm Red 7 seg display. They quote a very wide intensity range for 1mA and they don't quote a mtbf figure!
How to choose I don't know. I have an LCD panel in my TV and an OLED panel in my phone.
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Have a look at the attached Vishay datasheet for a 13mm Red 7 seg display. They quote a very wide intensity range for 1mA and they don't quote a mtbf figure!
How to choose I don't know. I have an LCD panel in my TV and an OLED panel in my phone.
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The newer LED displays are really fantastic compared to what we used to have "back in the day", red was the only colour. Then green and yellow, and those dimmed rapidly back then.
The problem with OLED displays is they have a comparatively short lifetime. I am absolutely less than thrilled my new Keysight meters are OLED. I'd be much happier with LCD any day. I wasn't a fan of the fluorescent displays in the 34401A meters either. They were far too bright from the factory, and yes, many have gone bad. THe HP 974A meter displays (LCD) are perfect, they need connectors cleaned very occasionally (just did one). The OLED display on my Keysight U1273A kills the battery quickly, looks nice. I don't care about looks.
LCD panels are pretty reliable, not sure about OLED yet. The Plasma ones in mine are still good, but I don't watch that much TV. They are heavy as sin, and hot.
The problem with OLED displays is they have a comparatively short lifetime. I am absolutely less than thrilled my new Keysight meters are OLED. I'd be much happier with LCD any day. I wasn't a fan of the fluorescent displays in the 34401A meters either. They were far too bright from the factory, and yes, many have gone bad. THe HP 974A meter displays (LCD) are perfect, they need connectors cleaned very occasionally (just did one). The OLED display on my Keysight U1273A kills the battery quickly, looks nice. I don't care about looks.
LCD panels are pretty reliable, not sure about OLED yet. The Plasma ones in mine are still good, but I don't watch that much TV. They are heavy as sin, and hot.
Plasma display panels are reliable, unfortunately they need high voltages switched very quickly in two dimensions so usually its the Plasma TV panel electronics that fails. Yes Plasma power consumption is too high for today's standards.
OLED's are an amazing technology, they seem to be reliable at least in comparison to the lifetime of a mobile phone.
Yes we are in agreement.
All I would say is that LCD is best for all round use, portable, low power etc. LED's are better for "important" displays that need to be checked often from nearby or from a distance and in any ambient light situation. I was using LED 7segment displays in my work back in the 1970's they were reliable and came in Red, Yellow, Green, Orange. Blue came after I think.
OLED's are an amazing technology, they seem to be reliable at least in comparison to the lifetime of a mobile phone.
Yes we are in agreement.
All I would say is that LCD is best for all round use, portable, low power etc. LED's are better for "important" displays that need to be checked often from nearby or from a distance and in any ambient light situation. I was using LED 7segment displays in my work back in the 1970's they were reliable and came in Red, Yellow, Green, Orange. Blue came after I think.
I can't get rid of my old Flukes either, since they all still work pretty well without any problems.
But I use my newer meters for critical work.
But I use my newer meters for critical work.