[David G4EBT]

Well that's a real showstopper Jeremy!

It's been an interesting thread, but really, Al's original query about the LT1021C and LT1236 designs was comprehensively answered by Mark Hennessy's response in post #2, though as you say, with ready made precision voltage references such as the one you cited being available so cheaply, it does beg the question, 'why homebrew?' and it makes no economic sense in this instance to do so. But then I don't see home-brewing as a diversion from restoration - I see them as twin aspects of my hobby.

Others have rightly questioned the relevance of the quest for precision to two decimal places, when for all practical purposes, it's largely an irrelevance to us as hobbyists.

The radios and other vintage electronics that we restore were made with components which - when new - often had a tolerance of +/- 20%, which does rather make it pointless to aspire to laboratory standards of accuracy. What the Precision Voltage Reference that I made was able to do, was to confirm to me that the cheap DMMs I own are quite accurate enough for hobbyists, differ little in their accuracy from one to another, and compare well to the 'big name' meters. Same goes for checking the calibration of my trusty Hameg 203-7 scope, on which - to me - the accuracy of the voltage calibration matters little as I mostly use it to observe waveforms - not to accurately measure voltages or frequencies.

Each to their own I guess.