well, it looks like my 8840A and 8840A/AF may be parts mules after all. i pulled the display boards out of both of them.
here's why the display doesn't light up on the 8840A: ![](http://u.cubeupload.com/worsthorse/IMG0982.jpg)
I am guessing this box got dropped hard on a hard surface at some point and when the display stopped working it was scavenged for parts, which is why it is missing all the micro-controller logic ICs, an A/D IC and one of the Fluke custom ICs.
and here's (at least one reason) why some of the buttons on the 8840A/AF don't work: ![](http://u.cubeupload.com/worsthorse/IMG0985.jpg)
Or you could use the money to get a nice 3478A and never worry about the display again... ![Wink ;)](https://www.eevblog.com/forum/Smileys/default/xwink.gif.pagespeed.ic.cldandycH0.png)
mnem
![Tweak :-/O](https://www.eevblog.com/forum/Smileys/default/smiliey_cal.gif.pagespeed.ce.yYMcAvxBJk.gif)
i could but i love these old flukes. such lovely, well-made gear.
so, about thirty minutes after i decided to part it out, i changed my mind. i figured
there had to be a way to get a working DMM out of these two boxes. so i decided to pull the ICs from the "working" Fluke into the one with busted display, install the cleaned display/keypad board, and see what happened.
damn if it didn't work.
![DMM :-DMM](https://www.eevblog.com/forum/Smileys/default/smiliey_dmm.gif.pagespeed.ce.CvRqtDiING.gif)
![](http://u.cubeupload.com/worsthorse/IMG0990.jpg)
maybe i will post all the intermediate photos of bench chaos later. at one point, both meters were completely torn apart and spread over the floor, so i could pick through the remains. after replacing missing parts, fixing some solder joints, and re-assembling, all the functions work, front and back connectors work and it detects that the VAC board is not installed. the display is also nice and bright. looks as good as my bench fluke.
![ThumbsUp :-+](https://www.eevblog.com/forum/Smileys/default/icon_smile_thumbsup.gif.pagespeed.ce._JElyJQqdB.gif)
here it is, mostly re-assembled:
![](http://u.cubeupload.com/worsthorse/IMG1001.jpg)
i found an option 09 board, too, which is on its way, and will bring the new meter completely up to grade.
still have to work through all the test and calibration procedures. glad i gave up on giving up on this one.
![Grin ;D](https://www.eevblog.com/forum/Smileys/default/xgrin.gif.pagespeed.ic.QVVz6XIT20.png)
edit: spent another thirty minutes at the bench comparing the new 8840A to the bench 8840A. from 10mV to 22V DC and from 10 to 10M ohms, it is within spitting distance. still, the self-tests indicate there's a problem in the DC section somewhere, so I will dig into that tomorrow. but overall this looks like a win.