On 08 Sep 2009 15:34:45 GMT, pete wrote:

Does anyone know of an online utility that can calculate
what combination of series and parallel resistors are needed
to get a particular value?
Specifically, I'm trying to calculate the best way to get
close to 5250 Ohm, using E12 preferred values. Power consumption
is not an issue and I'd like the value to be +/- 2% as that's
the resistor tolerance.

I'm not looking for the answer, I'm looking for the way to
find the answer. There are lots of websites where you can
tap in resistor values and have it calculate the result, but
that gets long winded. I've got a combination that gives
5253R with 4 resistors, but I'd like to do better

Use a spreadsheet.

Put the E12 values in a row at the top, and again in a column. At each
intersection of row/column put the formula for the combination you want
to try, i.e. parallel Rp = 1/(1/Rr + 1/Rc), or series Rs = Rr + Rc.

Pick the best result by eye.

OR

Take any 4k7 out the box. Measure it. Add approriate series resistor/s.
In the trade, this series resistor is labelled SOT (Select On Test).

Phil