What would cause death of a potentiometer

[cytt0rak]

Hello, I have built a pedal for friend of mine and its second time output pot is broken. I know they are not alphas, some no name chinese but I built many stuff with these and none of them broke yet. Am I just lucky or can a specific error after weeks of use kill it?

[drummer4gc]

Too much heat for too long when soldering it could significantly diminish the lifespan, particularly if they're cheapos.

[Plexi]

Too much heat, and sometimes the ears can loosen from the pot if it moves more.
That produce a bad/false lug/carbon track contact.

[EBK]

My money is on a bad solder joint plus mechanical stress.

[cytt0rak]

Too much heat for too long when soldering it could significantly diminish the lifespan, particularly if they're cheapos.

Too much heat, and sometimes the ears can loosen from the pot if it moves more.
That produce a bad/false lug/carbon track contact.

It could be true If it happened to years ago where I had bad mains type of soldering iron and with needle tip, I bought good soldering station with tips for soldering lugs,smt to increase efficiency.

My money is on a bad solder joint plus mechanical stress.

It could be but other pots on that pedal are not dead yet considering saturation pot is used more than output one. I use solid core wires to support components.

[EBK]

quote author=EBK link=topic=116837.msg1083354#msg1083354 date=1487345063]
My money is on a bad solder joint plus mechanical stress.

It could be but other pots on that pedal are not dead yet considering saturation pot is used more than output one. I use solid core wires to support components.
[/quote]
I was thinking more along the lines of a bad solder joint on a wire leading to the pot in question, plus the pedal getting bumped around enough to break the connection.

[cytt0rak]

quote author=EBK link=topic=116837.msg1083354#msg1083354 date=1487345063]
My money is on a bad solder joint plus mechanical stress.

It could be but other pots on that pedal are not dead yet considering saturation pot is used more than output one. I use solid core wires to support components.

I was thinking more along the lines of a bad solder joint on a wire leading to the pot in question, plus the pedal getting bumped around enough to break the connection.

Understood, I used a bit longer wires this time and tightened them that might take some stress off from wires and lugs. Thanks

[anotherjim]

Our usual carbon pots have low power handling. It is possible that for some reason significant current is going through that pot and burning out the track causing a dead spot, which could mean a fault in whatever else is connected, such as DC leakage on that other things input. If this output pot has it's wiper directly feeding the output (no cap or anything other than the bypass switch along the way), I would fit a resistor (maybe 1k?) in series to limit any such fault current.

[cytt0rak]

Our usual carbon pots have low power handling. It is possible that for some reason significant current is going through that pot and burning out the track causing a dead spot, which could mean a fault in whatever else is connected, such as DC leakage on that other things input. If this output pot has it's wiper directly feeding the output (no cap or anything other than the bypass switch along the way), I would fit a resistor (maybe 1k?) in series to limit any such fault current.

That was what I have been thinking at first, wiper is directly feeding the output should I put a resistor between wiper lug and and 1/4 jack or like a clr for led in front of strip lug?

[J0K3RX]

Tell your friend to stop stepping on the output pot... 

[EBK]

Tell your friend to stop stepping on the output pot... 

Good point.  That could do it too.

[anotherjim]

Yes, exactly like a CLR for a led.
But +1^, it is very tempting to turn a knob with a toe. In a perfect world, the knob would have a skirt that's just about clear of the case or pot nut so it doesn't rub, but would stop the pot shaft being pushed right down if stomped on. That's surprisingly hard to engineer when we can't choose an exact match between knob and pot. If the pot thread is too long to let the knob sit low, you could fit washers or spare nuts, assuming there's room behind the pot body.

[pinkjimiphoton]

too much current can smoke pots too. is your output cap leaking?

[robthequiet]

Ditto what Plexi said, the ears loosen up  -- factory spasm. Take that puppy out and inspect.