Potentiometer Values? - Page 1
Forum section: electronics / beginners

author: eruat
author_rank: Newbie
timestamp: October 20, 2014, 01:29:28 am
content: Hi Forum!So I've had some scratchy pots on my guitar amp. Decided to pull the board out and see what the situation is. Where I'm at, I can't see anywhere to squirt contact cleaning fluid.So, I've decided it's probably best to just solder in all new pots to increase the lifespan. Before I go out and buy some, just wanted to make sure I know what I'm getting.So, stamped in the back of each of the 6 pots is the following;1 2 3 4 5 6A10K B20K B2.2K B20K B200K B10KAs I understand, A and B mean the same thing? Both mean linear pots.. but just confuses me that I have an A10K as well as a B10K..So what do I need to know when buying new ones? What am I doing...?Thanks heaps for any help!!!

author: bills
author_rank: Frequent Contributor
timestamp: October 20, 2014, 01:35:24 am
content: deoxit is your friend, clean them.or in a pinch use wd 40. you can drill a small hole or spray it down the shaft.regardsbill

author: eruat
author_rank: Newbie
timestamp: October 20, 2014, 01:37:51 am
content: Quote from: bills on October 20, 2014, 01:35:24 amha! tricky!Thank you!

author: bills
author_rank: Frequent Contributor
timestamp: October 20, 2014, 01:47:34 am
content: To address your original post there are audio taper and liner taper pots among others.regardsbill

author: tautech
author_rank: Super Contributor
timestamp: October 20, 2014, 02:07:04 am
content: A & B mean "Logarithmic" or "Linear"http://en.wikipedia.org/wiki/Potentiometer

author: dentaku
author_rank: Frequent Contributor
timestamp: October 20, 2014, 02:16:55 am
content: By the way, are they regular big round metal pots.Those always seem to be wide open at the bottom like thisttp://www.o-digital.com/uploads/2226/2230-1/Rotary_Potentiometer_WH0171_1_6246_909.jpgI'm guessing your amp is more modern and has small completely enclosed pots if you say that you can't find anywhere to spray cleaner.Deoxit is the best stuff I've found too.If the pot that's labeled A10K is the volume then I would replace it with another pot of the same type. Volume knobs are usually logarithmic.

author: Richard Crowley
author_rank: Super Contributor
timestamp: October 20, 2014, 04:07:44 am
content: Quote from: eruat on October 20, 2014, 01:29:28 amIt seems quite unlikely that they are sealed pots, so there is almost certainly at least one place to squirt fluid into the pots. Post some photos of the pots if you want help identifying where potential openings are.QuoteIf they are standard 3/8 inch threaded panel-mount bushing pots, then you can probably find replacement pots as as long as they physically fit the space.But if the pots are PC-board mounted or some other more modern physical configuration, finding replacements may prove impossible.QuoteYour understanding is incorrect. "A" traditionally means "Audio" i.e. logarithmic, i.e "volume control"."B" traditionally means Linear for most other circuit applications.

author: vk6zgo
author_rank: Super Contributor
timestamp: October 20, 2014, 04:12:37 am
content: In Oz,(& I'm pretty certain,the UK).back in the day,linear pots were called "A" curve,& log pots were "C" curve.In the one of the silliest changes imaginable,now log is "A",& linear is "B".If your equipment is quite old,you can't necessarily trust the markings.Why the International community couldn't have come up with completely different alphabetical descriptions & avoided this confusion is beyond me!

author: eruat
author_rank: Newbie
timestamp: October 20, 2014, 04:15:52 am
content: Quote from: dentaku on October 20, 2014, 02:16:55 amI see now.Had only seen them on YouTube with the little hole seemingly designed to get sprayed into.They are exactly like that; they are mounted perpendicular to the board so you can't see the gaps. But could probably fit a spray tube up into them.Thank you very much, all! Case solved!

author: eruat
author_rank: Newbie
timestamp: October 20, 2014, 04:16:19 am
content: Quote from: vk6zgo on October 20, 2014, 04:12:37 amExactly what confused me!

author: Richard Crowley
author_rank: Super Contributor
timestamp: October 20, 2014, 04:47:00 am
content: It is trivial to actually measure the pots to confirm whether they are linear or logarithmic.And measure the end-to-end resistance value as well.So you don't need to trust the markings for value or law curve, either.But replacement seems like a poor substitute for cleaning the existing pots.Note also that noise could also be a result of DC current through the pot.From failure of a DC-blocking capacitor or two, for example.

author: Mr 12
author_rank: Contributor
timestamp: October 20, 2014, 05:20:11 am
content: I am a pedal steel picker and all you need do is soak them good with Deoxit.Most times if you look close you will see an opening where the pins come out of the case.Turn them upside down so you can load them with Deoxit inside the metal case then slosh it around a few seconds then drain out excess and let them dry out good.Deoxit evaporates quickly so it will not take long, maybe three minutes tops.I use a volume pedal so I took my pot apart and drilled a small hole in the back of the metal case so I can Deoxit them with a squirt of Deoxit with the little plastic spray tube on the can.

author: G7PSK
author_rank: Super Contributor
timestamp: October 20, 2014, 02:28:14 pm
content: Quote from: vk6zgo on October 20, 2014, 04:12:37 amBack in the day pots were marked Lin. or Log. there was no confusion. I still have a few lying around printed lin or log. Why the need for codes that then get changed every other day I don't know, god help us if the parts manufacturers ever get hold of an enigma machine, wait I think that they already have.

author: Dave Turner
author_rank: Frequent Contributor
timestamp: October 22, 2014, 08:32:07 pm
content: As Richard C stated it is relatively easy to measure the pot. Don't forget that in addition to log & lin pots one used to be able to obtain log-log and anti-log pots. Whether or not this is still true I haven't checked, but measuring them will determine what you need.