HeathBuilt EU-80A Voltage Reference Source: Fabricating a new "Voltage to Current Accessory"

This video is a sequel to my earlier video titled: "HeathBuilt EU-80A Voltage Reference Source: History, Restoration, Demonstration, Theory" When I restored and documented my EU-80A, it was missing the "Voltage to Current Accessory", and I was not able to find an original, so I fabricated an equivalent device, based on the HeathBuilt schematic, parts diagram, parts list and a photo of an original accessory. I used new parts with the same specifications as the originals, so the main difference between my version and the original is that mine uses a slightly smaller 'box' than the original. This video shows my research, design deliberations, fabrication steps, testing and final demonstration. Parts were sourced from Amazon (cast aluminum box & insulated BNC connector), Jameco (DPST slide switch), Digikey (male banana posts), Mouser (precision high-value resistors), and McMaster-Carr (insulators for the banana posts). I probably did not explain very well, in this video, exactly how I ended up verifying the accessory's 10nA output when none of my digital ammeters had enough resolution and/or a low enough current range to register such a low current value. I concocted a precision 1MΩ resistor from a resistor decade box in series with a small trim potentiometer, tweaked to be 1MΩ measured on my best meter. I put that resistance across the accessory's BNC output and powered the accessory with an accurate 10V, resulting in very close to 10nA, which dropped 10mV across the 1MΩ resistance, and that value I COULD measure. Timeline Table of Contents: 00:00 Introduction and history 01:46 Fabrication 44:00 Testing 46:49 Labeling the front panel 51:58 Beauty shot