A Potentiometer is really a variable potential divider and is a 3 pin device however by attaching the wiper to one end and forming a 2 pin device you now have a true 'variable resistor' or rather a 'Rheostat'. Regarding log and lin Pots the reason that in audio we use log for volume or signal level is that audio systems such as the human ear perceive audio volume asLogarithmic. Couple of bits of useless info !....cheers.
Hello Richard. Usually logarithmic potentiometers are used in audio applications. That is why there is also an "A" for Audio on the potentiometer. This is a little tip to recognize a potentiometer linear or logarithmic. I try to remember from my school days that the "B" stands for the linear type as "Balanced". Still nice to watch your videos again and also quite educational. Please continue with this, good learning experience and certainly a useful tool to learn how to detect and repair errors, although every technician has developed his own method, there is always something to learn from someone else. Greetings from Belgium. Andy.
Hi Richard. Just a little side note. There are also potentiometers on the market that are equipped with a small switch at the back. These are usually used in portable radios to turn the unit on and off and also to adjust the volume with the same button. These potentiometers are usually logarithmic. Still an instructive video for novice electrical engineers among us. Thanks GRTS Andy.
Yeah there are those ones, and also the ones that have a centre 'click' position or a continuous 'click' effect as you rotate them, usually achieve with a ball bearing and a ridged track
Just a little additional info. As well as A for "logarithmic" and B for "linear", if you have a pot with a C before the numbers (i.e. C50K), it means "counter clockwise" and if you see a W before the numbers (i.e. W50K), it means it has a "center detent". C and W just applies to circular potentiometers, not faders which only use A and B. If a fader has a center detent, it's usually just up to the manufacturers and sellers to list it as so and/or may have an additional part number for reference.
One other small point . There is a viscous lubricant in spindle which when you turn up the volume on an amp helps with tactile feel . If you clean with appropriate cleaner it stops the crackle but the pot then moves loosely around because the cleaner has removed the grease from the spindle. Not a problem for me but audiophile types are obsessed with the feel of equipment.
And there are various greases available to restore a dampened feel. Maybe not the very same fell as new from factory, but better than just cleaned and no lubrication.
Thank you. This was extremely helpful. I have some scratchy pots and was looking for ways to clean them. I would prefer that to replacing them. I too am a DJ. Rule #1 is no liquids near Mixer or amps. It eliminates so many problems. I even make my clients and their guests put drinks down before coming up to talk to me. Most totally get it right away, i just point at their drink and then at the power cords. Some you may have to tell them but either way works and keeps equipment safe.
I get linear faders and pots: The longer the distance, the higher the resistance. Just like wires. But how do log faders and pots work? Is there a different material being used which has resistance related to distance in a non linear fashion? What is it then?
Not wishing to be picky as I know this is a 'basics' video, but I recently learnt a potentiometer (by name and schematic drawing) is different to a variable resistor in that a potentiometer always have both track ends connected (potential divider) and all 3 pins connected to circuit, whereas a variable resistor (with the line through the component in schematic) only has 2 pins connected. At 3:53 I think you meant to not have one side grounded as the wiper is also grounded in that instance :)
And what exactly is wrong with having the wiper connected to the grounded end? All this will mean is that the variable resistor gives a DC resistance to ground that varies between the maximum value and zero ohms. That can be rather useful in some circuits, in fact the Bench PSU project I was working on a few videos ago has them connected exactly that way th-cam.com/video/-Bk2sgGXT6s/w-d-xo.html at 00:03:29 - check out RV1 and RV2 bottom left of the schematic. Not to be picky 😃but is there something wrong with that circuit? Because it works as intended when I tested it 😉
@@budgiefish It happens LOL. I didn't know about the info regards difference between potentiometer and variable resistor though, I thought the terms were interchangeable
Interesting but also worth mentioning lubrication - too much switch cleaner cleans the track but removes grease on the shaft used to provide smooth feel when turning. You can get remove and re-grease the shaft with appropriate lube.
I messed up a potentiometer by putting a bit too much contact spray in it. Now it's completely loose and really does not feel nice anymore. Would you know if it's possible to make them feel good again by maybe putting some fat in them or vaseline? Would be very useful for me.
Great video. I literally started out not knowing anything about Pots and have a great understanding now because of you. I do have a tricky situation though. I'm trying to replace the contrast Pots on an old tv and it's dual 20k 1k B. I can't find any with that combination. Have any suggestions?
Question to the experts in the comments: I have a old Fujitsu siemen's speaker system and i recall having trouble turning it on, sometimes it did, sometimes it didn't and i had to fiddle with the potentiometer and get lucky it turned on. Now i am trying to repair it and i took the covers off and had a multimeter reading on the potentiometer. The marking on the potentiometer are "A50k" and i had a reading of 30 ohms when it was at turned all the way up, and 0 ohms in every other position. Am i safe to assume the issue is the potentiometer and a replacement will fix it? Thanks in advance!
My potentiometer has a wire coming out from the opposite end of the prongs; do you know what it is for? The component was pulled from the LR balance on a 1980s stereo; Thank you!
I recently replaced ribbon cable as I had a missing right channel on my rack unit and after I replaced it not only two levels are matching when both input and output are maxed out but when I turn input fully left to mute input it squeals any idea why??
How do you fix a potentiometer (stepped gain switch with 22 variable resistance settings) that is not making full contact with the wiper? I have a neve 1073 style microphone pre amplifier in which the red gain knob has been knocked off track and spins freely the entire 360 degrees around the wiper track as opposed to catching on each value and stopping at its clockwise-most settings and counterclockwise-most setting. I’ve found if i pull the shaft out a bit it will make better contact and sometimes even return to normal. It still is working however takes some fiddling to get it to make contact and pass signal at the chosen resistance. I believe this is from corrosion due to it being a item I purchased second hand. Appologies if the terminology used here makes me sound clueless, I am clueless. Any input or help is appreciated, also never buy used items from guitar center 🫡.
Great video Richard. It's interesting looking at one of the log pots you tested, it had a totally uniform looking carbon track (Width and height wise). But it obviously measured as a log pot would. I wonder what the process is that they do to the carbon track to make it logarithmic. How do they make it more or less resistant without altering the width or the height of the track.
@@mikepanchaud1 use a terminal cleaner if it's really bad and THEN go back and either add a lubricant to it or use desoxit (it has lubricant added to it) if you don't lubricate it afterwards it will pretty quickly destroy the carbon film inside.
@@james1986 proooooobably, yes. It would definitely work as a lubricant, but you might need to spray them with regular contact cleaner first and then go back and apply the ACF50. (Which may be what you meant lol)
I have a Technics amp from the early 90's and the volume knob is a double joined pot, unfortunately one of the tracks has gone worn/faulty meaning that the volume is louder out of one channel, only way to correct it is to alter the balance, can't seem to find a replacement.
My newest Fluke leads in the past few years increase resistance very quickly. Fluke sent me a new set. The quality is difficult to find nowadays. Thank you for the education!
It used to be grandpa that would say things like “they don’t make things as good as they used to.” Now days, it takes as little as 6 months to notice this trend instead of a lifetime because planned obsolescence has morphed into plain old near immediate obsolescence.
Are they the TL175 (twistguard) ones? Same here, although they refused to acknowledge any problem last time I tried, so got replacements from Farnell, they've been replaced twice now, and the latest are also going high resistance, which is shame because otherwise they're really nice, long and flexible and twistguard is very useful :( I suspect they haven't made a proper electrical (soldered) connection in the probe handles, rather just crimped and overmoulded, as vigorous wiggling/bending the ends can restore low (sub 0.5 ohm) resistance where they can be upwards of 5 ohms in one instance ... probably dissimilar metals and galvanic corrosion in play.
Good job I didn't use it then. 🙂 I have in the past though and it sometimes worked. Could it be there are different types of switch cleaner (different formula from one brand to another)?
@Mr Guru Thank you for your explanation. Yes, I knew that much, but I have a repair job, where volume is controlled by a rotary encoder and it's intermittent and haphazard. In the middle of range suddenly it goes very quiet and stays there. I dismantled and cleaned it and put it together, checked all the solder joins and cables. Before I put the device together to test it (a lot of work), I thought I could check any additional components for faults. The signal path is complicated and travels through several boards. It's a rabbit hole. I just wanted to learn a typical circuit for the encoder, so I could easier reckognize the elements of it without reverse engineering half of the device.
@Mr Guru Yeah, I hoped for a possibly "typical" circuit for the rotary encoder volume control. I thought that maybe he repaired already such a circuit and he could explain it. Knowing my luck, as soon as I figure it out (and possibly film it for TH-cam as well), he will suddenly come across such job 😁.
![ILLSLICK X YOUNGOHM - We're The same [Official Video]](http://i.ytimg.com/vi/yUJNkobYR0E/mqdefault.jpg)
A Potentiometer is really a variable potential divider and is a 3 pin device however by attaching the wiper to one end and forming a 2 pin device you now have a true 'variable resistor' or rather a 'Rheostat'. Regarding log and lin Pots the reason that in audio we use log for volume or signal level is that audio systems such as the human ear perceive audio volume asLogarithmic. Couple of bits of useless info !....cheers.
Actually that is quite useful useless information 🙂
Hello Richard. Usually logarithmic potentiometers are used in audio applications. That is why there is also an "A" for Audio on the potentiometer. This is a little tip to recognize a potentiometer linear or logarithmic. I try to remember from my school days that the "B" stands for the linear type as "Balanced". Still nice to watch your videos again and also quite educational. Please continue with this, good learning experience and certainly a useful tool to learn how to detect and repair errors, although every technician has developed his own method, there is always something to learn from someone else. Greetings from Belgium. Andy.
Hi Richard. Just a little side note. There are also potentiometers on the market that are equipped with a small switch at the back. These are usually used in portable radios to turn the unit on and off and also to adjust the volume with the same button. These potentiometers are usually logarithmic. Still an instructive video for novice electrical engineers among us. Thanks GRTS Andy.
Yeah there are those ones, and also the ones that have a centre 'click' position or a continuous 'click' effect as you rotate them, usually achieve with a ball bearing and a ridged track
Thanks Richarrd for your replay. GRTS Andy.
Just a little additional info. As well as A for "logarithmic" and B for "linear", if you have a pot with a C before the numbers (i.e. C50K), it means "counter clockwise" and if you see a W before the numbers (i.e. W50K), it means it has a "center detent". C and W just applies to circular potentiometers, not faders which only use A and B. If a fader has a center detent, it's usually just up to the manufacturers and sellers to list it as so and/or may have an additional part number for reference.
I was actually hoping you would make a vid on pots.. thank you!
I think this vid has a variable potential and you may meet some resistance :)
😄😂
heavy resistance, especially with that bit that flirted off!
One other small point . There is a viscous lubricant in spindle which when you turn up the volume on an amp helps with tactile feel . If you clean with appropriate cleaner it stops the crackle but the pot then moves loosely around because the cleaner has removed the grease from the spindle. Not a problem for me but audiophile types are obsessed with the feel of equipment.
And there are various greases available to restore a dampened feel. Maybe not the very same fell as new from factory, but better than just cleaned and no lubrication.
Is it possible to rebuild carbon track in any way? I have an irreplaceable car throttle position potentiometer.
At 19:30 WRONG! Using *DeoxIT Fader F5* WILL repair it unless the carbon film is torn!
Thank you. This was extremely helpful. I have some scratchy pots and was looking for ways to clean them. I would prefer that to replacing them. I too am a DJ. Rule #1 is no liquids near Mixer or amps. It eliminates so many problems. I even make my clients and their guests put drinks down before coming up to talk to me. Most totally get it right away, i just point at their drink and then at the power cords. Some you may have to tell them but either way works and keeps equipment safe.
I get linear faders and pots: The longer the distance, the higher the resistance. Just like wires. But how do log faders and pots work? Is there a different material being used which has resistance related to distance in a non linear fashion? What is it then?
Not wishing to be picky as I know this is a 'basics' video, but I recently learnt a potentiometer (by name and schematic drawing) is different to a variable resistor in that a potentiometer always have both track ends connected (potential divider) and all 3 pins connected to circuit, whereas a variable resistor (with the line through the component in schematic) only has 2 pins connected. At 3:53 I think you meant to not have one side grounded as the wiper is also grounded in that instance :)
And what exactly is wrong with having the wiper connected to the grounded end? All this will mean is that the variable resistor gives a DC resistance to ground that varies between the maximum value and zero ohms. That can be rather useful in some circuits, in fact the Bench PSU project I was working on a few videos ago has them connected exactly that way th-cam.com/video/-Bk2sgGXT6s/w-d-xo.html at 00:03:29 - check out RV1 and RV2 bottom left of the schematic. Not to be picky 😃but is there something wrong with that circuit? Because it works as intended when I tested it 😉
@@LearnElectronicsRepair yes of course it's fine, doh - one of the pitfalls of commenting with a headache 🤕cranium contents deficiency...
@@budgiefish It happens LOL. I didn't know about the info regards difference between potentiometer and variable resistor though, I thought the terms were interchangeable
@@LearnElectronicsRepair The term that's being missed is 'Rheostat' you don't hear it much but that is a true 'variable resistor'
@@andymouse Oh I remember rheostats from 1960s and 1970s lighting control systems for stage/theatre productions
Interesting but also worth mentioning lubrication - too much switch cleaner cleans the track but removes grease on the shaft used to provide smooth feel when turning. You can get remove and re-grease the shaft with appropriate lube.
I messed up a potentiometer by putting a bit too much contact spray in it. Now it's completely loose and really does not feel nice anymore. Would you know if it's possible to make them feel good again by maybe putting some fat in them or vaseline?
Would be very useful for me.
Great video. I literally started out not knowing anything about Pots and have a great understanding now because of you. I do have a tricky situation though. I'm trying to replace the contrast Pots on an old tv and it's dual 20k 1k B. I can't find any with that combination. Have any suggestions?
Question to the experts in the comments: I have a old Fujitsu siemen's speaker system and i recall having trouble turning it on, sometimes it did, sometimes it didn't and i had to fiddle with the potentiometer and get lucky it turned on. Now i am trying to repair it and i took the covers off and had a multimeter reading on the potentiometer. The marking on the potentiometer are "A50k" and i had a reading of 30 ohms when it was at turned all the way up, and 0 ohms in every other position. Am i safe to assume the issue is the potentiometer and a replacement will fix it?
Thanks in advance!
My potentiometer has a wire coming out from the opposite end of the prongs; do you know what it is for? The component was pulled from the LR balance on a 1980s stereo; Thank you!
Well you flirting with potentiometers was more interesting than I expected it to be :)
Great Stuff! 😁
You can use them to find out the unknown value burned out resistors by substitution.
I recently replaced ribbon cable as I had a missing right channel on my rack unit and after I replaced it not only two levels are matching when both input and output are maxed out but when I turn input fully left to mute input it squeals any idea why??
Heya learned some more thanks
How do you fix a potentiometer (stepped gain switch with 22 variable resistance settings) that is not making full contact with the wiper? I have a neve 1073 style microphone pre amplifier in which the red gain knob has been knocked off track and spins freely the entire 360 degrees around the wiper track as opposed to catching on each value and stopping at its clockwise-most settings and counterclockwise-most setting. I’ve found if i pull the shaft out a bit it will make better contact and sometimes even return to normal. It still is working however takes some fiddling to get it to make contact and pass signal at the chosen resistance. I believe this is from corrosion due to it being a item I purchased second hand.
Appologies if the terminology used here makes me sound clueless, I am clueless. Any input or help is appreciated, also never buy used items from guitar center 🫡.
Another note: I believe it is a wire wound potentiometer. The pre amp is called the WA73
Great video Richard. It's interesting looking at one of the log pots you tested, it had a totally uniform looking carbon track (Width and height wise). But it obviously measured as a log pot would.
I wonder what the process is that they do to the carbon track to make it logarithmic. How do they make it more or less resistant without altering the width or the height of the track.
What I would think of is that it's a mix of carbon and filler, and they adjust the ratio while placing the track or something?
@@HauntedSheppard Yea, maybe they lay the log track first, then a second durable uniform layer on top, dunno.
what about the regular sliders (fader) vs a zero force fader ?
Like as in Scratch mixers?
Hello, how can we identify if a pot is logarythmic or linear?
Set the potentiometer at its mid point. If the resistance from one end to the center is about 50%, it is a linear pot.
To get rid of the crackling sound, can a potenciometer be cleaned with WD40? Thx
Don't use wd40, instead use switch cleaner which often cures crackles, sometimes permanently!
@@mikepanchaud1 use a terminal cleaner if it's really bad and THEN go back and either add a lubricant to it or use desoxit (it has lubricant added to it) if you don't lubricate it afterwards it will pretty quickly destroy the carbon film inside.
Would ACF50 work as a good lubricant or just be a dust collector?
@@james1986 proooooobably, yes. It would definitely work as a lubricant, but you might need to spray them with regular contact cleaner first and then go back and apply the ACF50. (Which may be what you meant lol)
I have a Technics amp from the early 90's and the volume knob is a double joined pot, unfortunately one of the tracks has gone worn/faulty meaning that the volume is louder out of one channel, only way to correct it is to alter the balance, can't seem to find a replacement.
My newest Fluke leads in the past few years increase resistance very quickly. Fluke sent me a new set. The quality is difficult to find nowadays.
Thank you for the education!
It used to be grandpa that would say things like “they don’t make things as good as they used to.” Now days, it takes as little as 6 months to notice this trend instead of a lifetime because planned obsolescence has morphed into plain old near immediate obsolescence.
Are they the TL175 (twistguard) ones? Same here, although they refused to acknowledge any problem last time I tried, so got replacements from Farnell, they've been replaced twice now, and the latest are also going high resistance, which is shame because otherwise they're really nice, long and flexible and twistguard is very useful :( I suspect they haven't made a proper electrical (soldered) connection in the probe handles, rather just crimped and overmoulded, as vigorous wiggling/bending the ends can restore low (sub 0.5 ohm) resistance where they can be upwards of 5 ohms in one instance ... probably dissimilar metals and galvanic corrosion in play.
Nooooo switch cleaner lifts the carbon and kills the track
Good job I didn't use it then. 🙂 I have in the past though and it sometimes worked. Could it be there are different types of switch cleaner (different formula from one brand to another)?
and what about deoxit f5 ?
Deoxit F5 is for faders / potantiometers you can use that but not the normal one it will kill the carbon tracks
@@LearnElectronicsRepair Deoxit Fader. Expensive, but I've used it for years and gives excellent results. Cleans and lubricates.
Hi Richard, could you possibly make a video about rotary encoders used as potentiometers? It would be MUCH appreciated! Regards, Jerry.
@Mr Guru Thank you for your explanation. Yes, I knew that much, but I have a repair job, where volume is controlled by a rotary encoder and it's intermittent and haphazard. In the middle of range suddenly it goes very quiet and stays there. I dismantled and cleaned it and put it together, checked all the solder joins and cables. Before I put the device together to test it (a lot of work), I thought I could check any additional components for faults. The signal path is complicated and travels through several boards. It's a rabbit hole. I just wanted to learn a typical circuit for the encoder, so I could easier reckognize the elements of it without reverse engineering half of the device.
@Mr Guru Yeah, I hoped for a possibly "typical" circuit for the rotary encoder volume control. I thought that maybe he repaired already such a circuit and he could explain it. Knowing my luck, as soon as I figure it out (and possibly film it for TH-cam as well), he will suddenly come across such job 😁.