Fluke 87 I, broken back-light


A couple weeks ago I bought a used Fluke 87 (original) multimeter that was supposed to work but where the back-light was broken. It was a good price because of the minor issue, and I almost never use the back-light on a multimeter, (I'd rather just change the battery often).

Fluke 87


When I got it is seemed to work just fine, so I thought I'd take a look inside.

Fluke 87 guts

Well I guess we'll be taking a close look...

Fluke 87 main board

One of the interesting things about the design of the meter is how the LCD panel is mounted. The data connections seem to be made through this soft, foam(?) mounting piece shown here. If you look closely you can see lines on the foam which are electrical connections, and multiple of them make connections with each pad that can be seen on the main board (previous image).

Fluke 87 LCD

Well anyway on the LCD mount the back-light power connection is made, and, as you may be able to tell from the super blurry picture, the header pins that make the connection have decided they don't want to be attached to the PCB anymore and have taken the pads with them.

Mischevious header pins on the back-light

The good news is we can fix this! I started by scraping off the soldermask to reveal the conductors, but there are two traces for one of the connections and both were joined at the pad meaning we needed two patch wires... or one bow-tie shaped wire wrapped around a new header.

Bow-tie bodginess

A little exposure to flux fumes and some reassembly and now we've got a still working new (to me) Fluke 87 with working back-light (that I'll never use.)

Basic Use

I love how the Fluke 87 series user interface just makes sense. Maybe it's because I've dealt the most with them though. I hadn't appreciated the subtle differences between the I, III, and V meters in the series though. The original does NOT have a separate battery compartment. In order to change the battery you have to completely open the meter up, its a little ridiculous. It's certainly not the worst thing in the world but its is such a desirable feature that when its not there, and you're used to it, it's almost painful. That said it is still a great meter, and it seems to agree with the readings of one of the Garage Physics Fluke 177's.

Meter comparison

I hope you're as excited for a massive meter calibration day as I am.