Re: Resistor in series


 

Tom,

Yes, I had anticipated that these NOS components might not have retained their specified values. I've been going through my father's effects while working on his scopes and finding all sorts of now-50-year-old components, some of which were expensive when purchased new, and thinking that some fair fraction of them are probably now terribly out of spec, if not completely destroyed (there are a number of big metal can capacitors that I know were stored for at least 20 years in a hot attic, and I don't have much hope that they are still in good condition). I purchased a dozen resistors in the hope that I could find two that were within spec.

Back in college I worked in receiving QC for a NASA contractor that built flight-rated systems. We would first receive a lot of 10 or 20 components of some description, which we would label and ship over to Goddard. They would eventually ship us back 2 or 3 components with paint marks and certification sheets, and we were required to use only those marked components in the parts we built for them. The other components we had shipped to them had been tested to destruction, and only the surviving 10% had been returned to us as flight qualified components. Careful selection of parts is something I have thought about ever since.

But what you're saying is that while my intuition was correct, the actual math makes a fool of me. I should really just use the metal film resistors when they arrive because they are lower noise and the inductance is a non-issue.

I can always gaze lovingly at the old Allen Bradleys. I'm quite sad that nobody seems to make resistors that have those nice sharp edges anymore (or, at least, I haven't found them for sale).

-- Jeff Dutky

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