1 quick question

[Neutral]

How do you replace a resistor with a trim pot, seeing as the later has three legs :?:

[petemoore]

leave open the outside [one of the] lug and connect the other two where the resistro would have gone.
  Or connect the wiper to one outside lug the other lug goes to the other side of where the resistor would have gone...from what I gather the reason for donnecting say lugs 1 and 2 together and lug three being the other side, is that this helps eliminate any noise from the pot.

[aron]

I always thought connecting one of the outer to the wiper was more for "safety" concerns....  :?

I have to admit, I rarely do this now, except for biasing circuits.... and always on amps.

[Mark Hammer]

It's for both noise AND safety.

Fact of the matter is that the wiper, as a movable part, runs the risk of being momentarily not in contact with the conductive element as you move it, or even *after* you move it.  It also runs the risk of corrosion over time (ever looked at a pot you've disassembled?  feh!!).

Both of these possibilities increase the risk that the wiper could make intermittent contact with the conductive element, acting like a switch as it goes from open circuit to whatever the preset resistance is.  By shunting the wiper and one outside lug, you guarantee that the MOST resistance it could ever provide under any circumstance is not open circuit but rather the maximum value of the trimpot itself.

Depending on the application, this could result in simply less chatter or intermittent-related noise, or it could reduce the risk of device failure if such intermittent contact produces sudden current draws and related heat.

Ultimately, it is not super-duper critical, but it IS good practice and doesn't really cost anything more than the price of the extra solder.

[aron]

it IS good practice and doesn't really cost anything more than the price of the extra solder.

Come on Mark, let me live on the edge!  :twisted: