Resistor nomogram

[boater sam]

Has anyone got a nomogram for finding parallel resistor values?  
I often shunt a resistor that is out of tolerance in a set with another to get back to the correct value and though its easy enough with a calculator a nomogram would be much quicker.

[ppppenguin]

If it's not far out you can approximate it in your head. For example if a nominal 330k reads 350k it's about 7% high. So you need about 15x 330k to get it right. Try 4M7. Then double check with calculator.

[djrm]

I always used kept a DOS program handy which found a combination of prefered values in parallel or serial to generate an arbitrary value. I don't know where that is now though. However here is an online version of something similar.
https://www.qsl.net/in3otd/parallr.html
hth David.

[joebog1]

https://www.omnicalculator.com/physics/p...l-resistor

That might help

Joe

[BusyBee]

I have used this occasionally in the past: Electronics Assistant

[boater sam]

Thanks all, some solutions there but a nomogram is faster than them all!
I may create my own, its a question of drawing exactly to scale on all 3 columns.

[djrm]

Thanks all, some solutions there but a nomogram is faster than them all!
I may create my own, its a question of drawing exactly to scale on all 3 columns.

When I was a boy my dad created something similar for a complicated calculas problem - i didn't understand at the time - still dont actually but I think I have the chart somewhere. This site has a useful looking nomogram creation tool: http://www2.ece.rochester.edu/~jones/Nom...mogram.htm

[Murphyv310]

I've never shunted an out of tolerance resistor in my life.
I could never understand why you would! Not only do old carbon composition resistors change in value they also get noisy.
A year or so ago I had to look at an old valve amp that produced a lot of intermittent noise, on opening it up there was around 10 or 12 bridged resistors that looked quite unsightly, I replaced all of them with the correct values, not only did the noise disappear but it looked far neater.

[boater sam]

Thanks all, some solutions there but a nomogram is faster than them all!
I may create my own, its a question of drawing exactly to scale on all 3 columns.

When I was a boy my dad created something similar for a complicated calculas problem - i didn't understand at the time - still dont actually but I think I have the chart somewhere. This site has a useful looking nomogram creation tool: http://www2.ece.rochester.edu/~jones/Nom...mogram.htm

Interesting, it will take me awhile to digest that!

[boater sam]

I've never shunted an out of tolerance resistor in my life.
I could never understand why you would! Not only do old carbon composition resistors change in value they also get noisy.
A year or so ago I had to look at an old valve amp that produced a lot of intermittent noise, on opening it up there was around 10 or 12 bridged resistors that looked quite unsightly, I replaced all of them with the correct values, not only did the noise disappear but it looked far neater.

I use the technique mainly as a diagnostic tool. As I don't get involved with many HiFi amps the noise factor is not a prime consideration.
Where I have shunted resistors on a permanent basis is when hiding a small correction resistor behind a large original in a set that I am eager to conserve appearance  originality.