potentiometer question

[ArtOfShred87]

what is the little piece of metal on certain pots for? is it a ground? ive never seen this before.

[Tom Phillips]

That tab fits into a hole in the panel and prevents the pot body from turning in the shaft mounting hole. It is usually only seen on better quality pots. Kide of a belt & suspenders type thing.

[guitarmike2107]

Most machined chassis dont have the holes for these, so people end up snapping them off.

heres a chassis that does have the location holes

[Mark Hammer]

I don't know if they are unique to better pots, but they are certainly more likely to be used in better quality builds.

Think of it as another form of strain relief. If the pot gets a little loose, such that turning the knob results in moving the pot a little this way and that, eventually any wires soldered to the pot may fracture from the bending.

Personally, I just snap them off, because I find it easier to not machine for the hole. Instead, I provide the strain relief by slipping a piece of shrink wrap over the sire and lug after soldering it in place. Wire can still fracture inside the shrink wrap if the pot is jiggled back and forth enough, but the likelihood is reduced. Use of locking washers on the inside of the chassis (i.e., against the physical casing of the pot itself, rather than on the outside under the nut) can also help a great deal in preventing lateral movement.

Of course, in those instances where there is legending on the outside of the chassis (1, 2, 3, 4,......11!), and the knob is pressed onto the pot shaft, and can only have one orientation, use of the tab helps to assure that the knob pointer, and the legending, always line up right.

[jrfrond]

I like making use of the locator tab on pots on new builds. It keeps things from getting twisted up and broken.

I always like to use double lockwashers (one on each side) to help keep a pot from loosening. Either that or a drop of LocTite 222 on the threads. I also NEVER rely on the mechanical connection for a pot ground. Have seen far too many pot-borne grounding issues over the years, either from loosening, or oxide buildup from galvanic reaction between the pot body and chassis. On vintage resto work, I will usually loosen each pot and run a couple of drops of Stabilant into the chassis contact point, to ensure good ground contact.

[Ronsonic]

On vintage resto work, I will usually loosen each pot and run a couple of drops of Stabilant into the chassis contact point, to ensure good ground contact.

Good practice.

Not so retro - there are some recent-ish Marshalls that depend on having the Footswitch jack grounded for the channel switching to function correctly and not become hopelessly confused. Those can be hours of fun until you figure that out.