[William Dudley] picked up a Fluke 8840A bench multimeter at an auction, but was unfortunate to find out that it was reading resistances inaccurately. It was also lacking the optional board to enable AC measurements. Desiring to use the usually lovely meter, he established about restoring and upgrading the machine.

Thankfully, the 8840A was from a time when Fluke employed to overtly publish schematics in its manuals. Consequently, mixed with getting a appear at some photos on the internet, it was uncomplicated for [William] to recreate the primary AC “Option 09” board to enable the wished-for functionality. As is normally the way, his efforts didn’t operate initial time, but after some bodge wires had been put in, all was effectively. [William] reviews the measurements are “reasonable, maybe even sufficient” with no calibration carried out.

Restoring the resistance difficulty was quick. It turned out to be corrosion on the selector switches, discovered when high-resistance measurements were being precise, but low-resistance measurements weren’t. A bit of flick-flacker with some make contact with cleaner sprayed into the switches acquired issues performing all over again nicely.

It’s pleasant to see old components restored to entire features, notably when it’s as desirable and properly-designed as an previous Fluke meter. Bringing back again aged instruments from the useless? You know we wanna listen to about it!