Blog reader “Dmitri” has sent pictures of a very unique and interesting modification he performed on his recently acquired Fluke 8060A. The LCD was ruined, so he has fashioned a replacement using green SMD LEDs arranged to form 7-segment numerals, with light dissipating film and protective acrylic from a broken iPhone. The mask was cut with a German desktop milling machine. The new display board was connected to the processor sub-board with the same kind of teflon-insulated wire used to connect the LEDs and ballast resistors.
There seems to be a trend in Fluke repairs here lately. Other than your occasional fusible resistor, the problems seem to be related to materials instead of electronic bits. Cracked and broken plastic, and metal fatigue. Are these design problems, or is it that people use these devices so heavily for so long, that the finite lifetime of these metal and plastic parts is exceeded? Well you be the judge of that, I’ll just look for a way to make repairs.
Today’s issue concerns the jack assembly for the Fluke 80-series of DMMS including the 83, 85, 87, and 88 models. Instead of individual 4mm banana jacks, there is a single molded assembly containing all four jack ports. Each jack consists of two half-round contacts inside a red or black colored shroud. The two separate contacts are used to detect when a plug is inserted in the A or mA jacks on the left side. Inserting a plug shorts the two halves, which is detected by the meter and results in a chirping sound when the rotary switch is set for anything other than current measurement.
Recently someone asked how I get the old used multimeters featured in these blog posts to look shiny and clean. For the most part, the answer is surprisingly simple: disassemble, scrub parts with soap and water, dry, and re-assemble.
But of course there are many details. Results are rarely perfect with used equipment, but lots of improvement can often be achieved. The normal published photo size on this blog is 1024 x 768, which hides some imperfections. Here’s a couple of before and after photos with a little higher resolution. Neither of these are perfect, but the improvement is worth the effort.
Posted in How-To
Tagged DMM, Vintage
Happy New Year 2014! Doing some housekeeping and software updates, found this information was buried in the photo galleries.
Here’s how to remove the knob on a Fluke 70-series DMM (the older, rectangular-style meters.) This includes the original and series II models 75, 76, 77, 79, 21, 23, 29, and similar.
Not much repair activity lately, but in honor of Halloween, note that a photo gallery of cheap multimeters of the “Harbor Fright” variety has been posted. New also is a quick look inside the Weston 6100 Roadrunner.
The Fluke 26-III and 79-III models are identical except for the model number. This model adds some extra features not available on the 77-III (and its identical twin the 23-III), like frequency and capacitance measurement, 4000 counts vs. 3200, RMS response, and a faster update speed. It also has a special 40-ohm resistance range that provides 10 milli-ohm resolution, aimed at electricians who may want to measure and compare contact resistances on relays and switches. It’s not a bad tool for the electronics workbench either, provided you do not need precise measurements of current in the micro-amp range. It does however have 1μA resolution in its lowest current range (4mA).