Grundig 80U

[Terry]

Red black black orange space red? 200K 2% right? .

I bet the original wasn't 2% Amie!

Just looking at the values on that schematic, I'm surprised that they don't follow the usual logarithmic series, widely used  here since before the war. Yet, with FM coverage, not to mention the valve line-up, that set is well post war.

'Preferred values' started off with 6 values per decade and a tolerance of ±20%. As manufacturing methods improved, ±10% tolerance was easily achievable and the number of values increased to 12. These series are known, respectively, as E6 and E12 - I'm guessing here but the E probably stands for exponential.

Other ranges with even tighter tolerances and values per decade exist - thus your 200k ±2% samples - and ±5% seems to be the norm these days but, for all but rare instances, for the vintage kit we are discussing here, the E12 range is sufficient.

I created a chart some years ago to illustrate the three main series and how neatly the tolerance of each value butted up neatly with the next value in the series. I thought I'd posted it here but can't find it so here it is and another for illustrating the maximum voltage for each power rating:





Note the maximum voltages highlighted in yellow. Some manufacturers can provide resistors with higher voltage limits but they are very rare.

If you look at the range of values - all, except the volume control, as far as I can see in  round figures - you will see that there is no rhyme or reason for using them instead of standard values.