I have an ancient Fluke 8060a that the display has been out for many years.
I ran across it in the shop the other day. After searching the internet for an LCD display for it for most of the afternoon and coming up empty, I was about to throw it out.
There were some web pages about rewiring the leads and attaching a different LCD display, but it seemed like a lot of work. And I have two other Fluke meters, so no worries.
But before I threw it out, I decided to just take it apart and see if I could see anything obvious. There wasn't anything obvious, it was pretty clean, the board looked ok, there was very little dirt and no residue of any type that I could see.
But just for grins, I decided to clean the contact area on the LCD with alcohol, do the same for the connector side, and put it back together.
To my amazement, when put back together it works perfectly!! The LCD, which had maybe two segments you could read, is now just like brand new!
So long story to say I learned a lesson! Those old LCD displays may not fail as often as they appear. They just lose good contact and need a little cleaning.
gabo
I ran across it in the shop the other day. After searching the internet for an LCD display for it for most of the afternoon and coming up empty, I was about to throw it out.
There were some web pages about rewiring the leads and attaching a different LCD display, but it seemed like a lot of work. And I have two other Fluke meters, so no worries.
But before I threw it out, I decided to just take it apart and see if I could see anything obvious. There wasn't anything obvious, it was pretty clean, the board looked ok, there was very little dirt and no residue of any type that I could see.
But just for grins, I decided to clean the contact area on the LCD with alcohol, do the same for the connector side, and put it back together.
To my amazement, when put back together it works perfectly!! The LCD, which had maybe two segments you could read, is now just like brand new!
So long story to say I learned a lesson! Those old LCD displays may not fail as often as they appear. They just lose good contact and need a little cleaning.
gabo
A while back my Fluke 8050A also developed a wonky display. Disassembled, cleaned board and display contacts, reassembled, works perfectly. Ready for another 40 years of service.
It is great, with the 4½ digit display, RMS bandwidth 100kHz, the 300M resistance range, and readout in dB.
I'd hate to have to pitch it, originally cost $500.
I'd hate to have to pitch it, originally cost $500.
Last edited:
I may have to recap mine now. The caps all look good right now, but they are old. Now that it's working perfectly I can recap and prevent any long term problems.
Like someone else said, it'll be ready for another 40 years of service!!
gabo
Like someone else said, it'll be ready for another 40 years of service!!
gabo
I'm not a rabid re-capper, but experience has taught me that, with most of the well aged equipment I use, it may be a good plan.
Both of my Keithley meters (177 & 173A) recently had to be re-cap'd due to shorted electrolytics, one of which took out a pass transistor in the power supply. And to be clear, these were not cheap chinese caps, we're talking top grade parts with epoxy end seals. Clearly, nothing lasts forever!
So, figured while I'm at it, I'll do all of my meters and get it out of the way.
It turned out to be quite a list; I'd never realized just how many different meters I use for everything
Both of my Keithley meters (177 & 173A) recently had to be re-cap'd due to shorted electrolytics, one of which took out a pass transistor in the power supply. And to be clear, these were not cheap chinese caps, we're talking top grade parts with epoxy end seals. Clearly, nothing lasts forever!
So, figured while I'm at it, I'll do all of my meters and get it out of the way.
It turned out to be quite a list; I'd never realized just how many different meters I use for everything
There is an issue with leaking caps with these if you do some searching. Whether it was just a bad batch or not I'm not sure, but a lot of these have caps that have leaked electrolyte all over the boards. Mine was in fairly bad shape and the board was a bit beat up by the time I was done. I was surprised that it actually worked so well after I got it all back together. There are some great guides posted on refurbing these.
Yes, good points. In looking at the meter there are really only about 8 or so electrolytic caps there. All common values that I already have in the shop.
So you've given me the incentive to pull it apart again and replace all the caps. Thanks for the inspiration!!
gabo
So you've given me the incentive to pull it apart again and replace all the caps. Thanks for the inspiration!!
gabo
photo of a Fluke 8050A I converted to LED's
forty wires! the 7805 regulator gets a bit warmer so put a small heatsink on that (20mm bolt), increase size of unregulated supplies capacitors to 1000uF (reduce ripple),
the DP's and the -ve sign work, didn't bother with the other indicators,
didn't like the power on/off switch because it runs the unregulated supplies right through the main PCB and the display PCB to get to the switch and the line transformer is always left on, wasn't bothered about relative measurement so the Power and Relative switches have gone,
I used common Cathode LED's and no series resistors! the leading "1" needs a little help from a pull up resistor to get the brightness right, the -ve sign needs a PNP transistor to work properly,
be careful working near the CPU chip, its very close to the unregulated supplies,
forty wires! the 7805 regulator gets a bit warmer so put a small heatsink on that (20mm bolt), increase size of unregulated supplies capacitors to 1000uF (reduce ripple),
the DP's and the -ve sign work, didn't bother with the other indicators,
didn't like the power on/off switch because it runs the unregulated supplies right through the main PCB and the display PCB to get to the switch and the line transformer is always left on, wasn't bothered about relative measurement so the Power and Relative switches have gone,
I used common Cathode LED's and no series resistors! the leading "1" needs a little help from a pull up resistor to get the brightness right, the -ve sign needs a PNP transistor to work properly,
be careful working near the CPU chip, its very close to the unregulated supplies,
Attachments
PS. the ten LED Common Cathode pins (two pins per LED) are wired to the -5V line,
wire count:-
segment wires 4x7 + 1x3
decimal point wires 4
Common Cathode wires 5
hard wire -5V and DGnd lines from main PCB to display PCB, wires 2
wires between main PCB and display PCB, W,X,Y,Z,DP,ST0,ST1,ST2,ST3,ST4, wires 10
break the unregulated lines to prevent them leaving the main PCB, break the BP wire connect it to the -5V line on the display PCB,
FLUKE 8050A bench DVM LED Display
wire count:-
segment wires 4x7 + 1x3
decimal point wires 4
Common Cathode wires 5
hard wire -5V and DGnd lines from main PCB to display PCB, wires 2
wires between main PCB and display PCB, W,X,Y,Z,DP,ST0,ST1,ST2,ST3,ST4, wires 10
break the unregulated lines to prevent them leaving the main PCB, break the BP wire connect it to the -5V line on the display PCB,
FLUKE 8050A bench DVM LED Display
Thanks very much Rich for your very helpful 8050A LED mod info. After inheriting an 8050A with a faulty display I found several LED mods online but yours appealed with common cathode LEDs and absence of series resistors.
Following your notes I successfully modded my 8050A so thanks! If you happen to see this post could you assist with an issue I had with the PNP "minus" driver. I was unable to get this to work and wondered if you could provide any assistance?
Here is my completed 8050A:
Following your notes I successfully modded my 8050A so thanks! If you happen to see this post could you assist with an issue I had with the PNP "minus" driver. I was unable to get this to work and wondered if you could provide any assistance?
Here is my completed 8050A:
To the original fault, cleaning these displays, PCB and connector with IPA is a common fix for LCD displays. So you did the right thing.
We cleaned so many Fluke meters to restore their displays in the cal lab, you just expected this when seeing one for calibration. Even one flickering segment or digit. Many modified meters probably only needed cleaning.
We cleaned so many Fluke meters to restore their displays in the cal lab, you just expected this when seeing one for calibration. Even one flickering segment or digit. Many modified meters probably only needed cleaning.
I should perhaps try cleaning my own 8060A once more. I had done it before, but it later began playing up again. I currently have it on ice, with the intention of doing the display mod, eventually. Love this meter.
Yes ! Those 8060A are indestructible ! I still have mine... Among other FLUKES.
T
T
Good to know that your Fluck meter is working now. Kudos! You fixed it. If you have the Fluke 5700/5720/5730/5790 meters, you may want to make a repair extender board like this: https://www.pcbway.com/project/shar...5730_5790_repair_extender_board_b5ff927f.html
Extender board adapter aids repair and troubleshooting of Fluke 5700A, 5720A, 5790A, 5730A, 5790B, 5500A, 5520A meters.
The Fluke 5700A / 5720A etc are multifunction calibrators. I used them in the lab. Wish I had one of my own!
I like the Fluke meters, but the HP / Keysight models are better. Keithley makes a fine product also. If you grab an HP 34401A you have about the best bench meter ever.
I like the Fluke meters, but the HP / Keysight models are better. Keithley makes a fine product also. If you grab an HP 34401A you have about the best bench meter ever.
Thanks for your kind comments. I will explain referring to the mod circuit attached and the photo attached in case there's a misunderstanding somewhere.
-U10 is removed
-all 7seg common cathodes are connected to 0V, 7seg Anodes are pulled down towards -5V to turn them on, current limited by the CMOS IC's
-BP signal from J1 is cut/removed
-Pins 2, 7, 8 of U11 6, 7, 8 of U12 6, 7, 8 of U13 6, 7, 8 of U14 6, 7, 8 of U15 2, 7, 8 of U16 are all connected to the negative 5V (-5V) supply.
-Pin 6 U11 is connected to most significant 7seg segments b and c. The 2K7 resistor between pins 16 and 6 of U11 adjusts brightness (leading "1")
-The leading "1" lights up when pin 6 is low (-5V)
-Pin 5 of U11 I call + sign is connected to the PNP emitter that way the - sign can only display when pin 5 is low (-5V)
-the PNP collector is connected to seg g of the most significant 7seg (the middle "-" segment)
-the PNP base is connected to pin 4 of U11 via a 3K9 resistor
-the PNP transistor is a KSA733GTA (or just A733) its a low current high hfe PNP transistor
When the "+" pin 5 is high it keeps seg g off, current flows from emitter to base keeping base close to 0V and seg g off. When pin 5 is low seg g is directly controlled by the "-" on pin 4. When pin 4 pulls down to -5V current flows from seg g through the forward biased collector base, through the 3K9 resistor and into pin 4 which is at -5V so the - is directly controlled by pin 4 and its brightness is set by the 3K9 resistor.
If you want you can leave out the PNP but the - sign comes on when you don't want it to.
Hope that explanation is correct and it helps you get it working. The attached photo I took this morning confirms the circuit mods.
Good luck
Rich
Attachments
Thanks Rich for the follow up. It appears that U11 in my meter has a faulty pin 4 output. I'll check it out further.
Again thanks for taking the time to chronicle your approach to getting the old Fluke DMMs operational.
Again thanks for taking the time to chronicle your approach to getting the old Fluke DMMs operational.
Yes after some more checking, U11 turned out to be faulty. As I had never seen the unit working due to the faulty LCD display I suspect U11 was faulty when the 8050A came to me....