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

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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 only sell on eBay under a nickname:
grudn_2015

The LED display module is sold here:

https://www.ebay.com/itm/154780459035


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 (Vss) since there is not a ground (Digital LO) connection to the display driver board?

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