trim pots in series = ?

[tungngruv]

I need a 20k trim pot. Is it possible to hook up two 10K trimpots in series and get 20K resistance, like hooking up resistors in series adds resistance? Thanks for any help in advance.

[RandomRedLetters]

yes, its totally possible. To make it easier, have both on 0% then adjust just one, and once thats 100%, then start adjust the other, just to keep track more easily.

[RickL]

That will work if the trim pot is used as a variable resistor but not if it's wired as a voltage divider.

Two possibilities come to mind if you don't have a 20k trimmer and it has to be set up as a voltage divider: use a bigger trim (i.e. 50k) with a parallel resistor across the outside lugs; or tack 4.7k resistors to each end of the 10k trim. This will only let you adjust in what would have been the middle part of the 20k but if you end up at one end of the trim range and need to adjust more set it up with the 10k trim on one side and a 10k resistor on the other end.

[Mark Hammer]

Rick's suggestion of the trimpot+resistor combination is spot on.  If you know approximately what range of the trimpot will be most needed, you can choose appropriately.  For instance, if I knew I needed a 100k trimpot but the middle range would be used far more than the extremes, I could use a 50k trimpot (likely 47k) with a 24k to 27k fixed resistor on either side, or even a 25k with a 36k-39k resistor on either side.  The circuit itself doesn't really care where the resistance comes from, merely that it is there.  Your goal is to be able to provide the required resistance and the required degree of adjustability.

[tungngruv]

Thanks everyone!!!!

[petemoore]

I get 10k's to bias Q2 FF, but 'bump' it up to adjusting between say 5k6 to 15k6 by adding a 5k6 resistor to it.
 pots sometimes do exactly what you want, other times I just add a little here, take a little off there...
 Most of those pot mods are a resistor added to an outside lug or a resistor across lugs 1 and 3.
 I like to see what the actual resistance of the pot is, with the DMM ranged to R and across the outside lugs.
 Then sometimes if it matters and I have a choice I'll clip one dmm lead to the wiper and then see what halfway measures on each side.
 I've had some bad pots so while I'm checking the taper, very slowly, I'm also looking for dead spots on the pot.