04-05-2017, 08:46 AM
Back in the late 60s I prided myself on the breadth and quality of the component stock I had built up and sold large numbers of them.
However, there were limits. I could see no point in stocking resistor values beyond the E12 series as these were perfectly adequate for our service purposes and the constructional articles in magazines that our component buyers wanted them for.
However, many of these project designs came from engineers working on professional and military electronics at places like Marconi. I'm quite sure that a lot of the designs were based mainly on rule of thumb calculations or mental arithmetic as the proliferation of 1k, 2k2 and 10k values for collector load resistors appeared to indicate. There was, of course, another commonly used value which supported this theory: 5k1 ...
A succession of boys, mainly from the local grammar school, got a crash course in tolerances when they asked for 5k1 resistors - fortunately most turned up with the relevant magazine in their hands so I was able to point out to the statement at the bottom of the component list which said "All resistors ½W, tolerance ±20% unless otherwise stated" and prove to them that my 4k7 ±5% resistors were guaranteed to be much closer to 5k1 than a resistor of the 'correct' value with a tolerance of ±20% - even assuming that such a component even existed anywhere on the planet!
The fun began when a bewildered mum turned up in the workshop holding a piece of paper on which her son had copied out the list of values he wanted her to buy ...
However, there were limits. I could see no point in stocking resistor values beyond the E12 series as these were perfectly adequate for our service purposes and the constructional articles in magazines that our component buyers wanted them for.
However, many of these project designs came from engineers working on professional and military electronics at places like Marconi. I'm quite sure that a lot of the designs were based mainly on rule of thumb calculations or mental arithmetic as the proliferation of 1k, 2k2 and 10k values for collector load resistors appeared to indicate. There was, of course, another commonly used value which supported this theory: 5k1 ...
A succession of boys, mainly from the local grammar school, got a crash course in tolerances when they asked for 5k1 resistors - fortunately most turned up with the relevant magazine in their hands so I was able to point out to the statement at the bottom of the component list which said "All resistors ½W, tolerance ±20% unless otherwise stated" and prove to them that my 4k7 ±5% resistors were guaranteed to be much closer to 5k1 than a resistor of the 'correct' value with a tolerance of ±20% - even assuming that such a component even existed anywhere on the planet!
The fun began when a bewildered mum turned up in the workshop holding a piece of paper on which her son had copied out the list of values he wanted her to buy ...
