Another capacitor question

[Terry]

If you read through a lot of the forum threads you will find that folks with less experience worry about tolerances far too much ... 

I tried to dispel this worry some time ago and explode the myths surrounding tolerances in this VRAT thread

One thing about resistor values, in particular, which confuse the novice is the seemingly random sequences of values whereas if to look at the chart I drew (reproduced below) you an clearly see how cleverly the values where chosen to neatly produce a continuous sequence, irrespective of tolerance.

... Old components were  never made to close tolerances, it cost the set makers too much brass. Rarely did they use any resistors better then 20%, paper/wax caps were possibly worse, hard to tell as they are mostly duff now, and what few electrolytics they used were as bad as +100%/-50% and they were expensive then ...

I would guess that early E6 batches were made by guesswork and the value allocated by measurement afterwards.

I you look at the early colour code - body - tip - spot instead of the later rings - this might give us a clue.

Say you intended to produce a batch with values of around 500Ω, say.

Now measure them. Analogue meters would be used, of course, so it would make sense to have scale with 6 divisions on it, one for each value in a decade, as the absolute value didn't matter anyway! You don't need values, either - colours will do!

So resistor one falls in the orange sector - dip it in the orange paint pot and hang out to dry. The next one scores blue, so dip it in the blue paint pot and leave that out to dry, too. Now one scores in the yellow sector - repeat using the yellow paint pot this time.

When this initial sorting is finished, each resistor will have body colour corresponding to the first figure of its value. Resistors painted red or orange can skip the next stage, because the second digit of their value is the same as the first but the rest will have one end dipped in the appropriate colour for this value, so the blue ones will be dipped in grey paint, the yellow ones in violet paint and so on.

Finally, all of the resistors will have a brown spot added to complete the code.

Easy, Innit?

Care would need to be taken with the first two segments, as they would both be black, and the resistors would have to be segregated during the drying phase so that they received the correct second colour and further care would be needed where selections crossed the decade barrier to ensure the correct spot was added but each procedure could be carried out  very rapidly, which would be vitally important, of course.