[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,