# How to clean a dirty pot?



## Denim

I have a Yamaha integrated amp since the early eighties. It developed a problem years (decades) ago with the volume knob. I usually listened with the knob always in the same position. Now you get noise at that same position. I've tried tuner shower, but it's only a temporary fix. Is there another technique I can try, short of replacing the pot? I'm assuming it's a pot.


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## bhjazz

It's very likely a pot. You'll need to get inside the amp and spray some contact cleaner inside the pot. Twist profusely (the pot, not your body.) I've used Zerosolve. Be careful that it doesn't drip all over the rest of the unit. Hey, you can slo get some canned air and clean off any dust inside that may help keep heat on stuff. 

 No guarantees. I've had this work for an extended amount of time, but seemed to come back. I hate it! 

 Good luck!


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## Denim

That is what I have done in the past. The noise always comes back. I looked into replacing the pot several years ago. I may have another try at that. Otherwize, I'll sell it and move on.


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## gsteinb88

You could always just replace the pot. Its probably just a ganged 10k-100k pot...its what i need to do to my marantz
 -g


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## PinkFloyd

Replace the pot, they're as cheap as chips. If you can upload a pic of the guts we can identify which one you'll need.


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## mono

If you are an uber-cheapass like me, you might try refurb'ing the pot. OK, it wasn't my original plan but when I find a pot acting up, it's gotta be pulled off the board anyway to replace it, so while it's off I pop the thing open, put a little more tension in the wipers, rub on the tracks with a dry paper towel and polish the wiper contacts with a special tool I call "Q-Tip-With-Dried-Brasso-On-It". All kidding aside, dried brasso is good for cleaning some things as it's less abrasive, less messy.

 So about 3 minutes later I've finished and try it- usually works pretty good. Some pots are riveted shut though, that's more involved that I'd want to get before giving up on it because I don't have a teeny rivet gun or tiny screws that long.


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## Craftsman

Straight contact cleaner never works for long on cleaning a pot. In addition, I always (I mean ALWAYS) find that the pot never "feels" the same afterwards....

 What I've used for the past couple of years is a CAIG product called DeoxIT FaderLube (formerly known as Cailube MCL). An application or two of this stuff as well as moving the knob full cycle does wonders for the sound. No static, noise and the pot remains silky smooth....


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## Denim

Here is a top down view of the pot 





 The piece of paper on the back of the pot says "MI00KnY". At first, I thought it was 100K. The pot in on the main vol board 
	

	
	
		
		

		
		
	


	



 It has 6 pins soldered to the board (2 X 3).

 If I get past the noisy pot problem, I will move to the tuner next. It won't remember the station memory. Possible bad cap. Never could find anyone to identify it.


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## Denim

Here is a better view, but out of focus shot


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## gsteinb88

Looks like it should be simple to replace. Just pop off the knob, lift it out, unsolder it, solder in the new one, put on the knob and you are ready to go. If you want to check the resistance of the pot, measure from one side to the other (as opposed to one side to the center).
 -g


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## Denim

Quote:


  Originally Posted by *gsteinb88* 
_Looks like it should be simple to replace. Just pop off the knob, lift it out, unsolder it, solder in the new one, put on the knob and you are ready to go. If you want to check the resistance of the pot, measure from one side to the other (as opposed to one side to the center).
 -g_

 

I agree that it shouldn't be too hard to do. The board that the pot is mounted on does not have much slack on the ribbon cable, but I can turn it over. I'm hesitant to remove it because I don't know if I can find a replacement. I guess I'll never know until I take it out and measure the resistance.


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## gsteinb88

That thing has its back riveted on, so you are going to have on hell of a time cleaning it. Even if you cant find a replacement, there are two options. One, solder that pot back in, and two, get a pot of a close, but different value. You _will_ be able to find one of close to the same value, if not the exact same.
 -g


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## Denim

Thanks for the response. I've got a bit of learning to get a close match. My first step is figuring out the size. Is it measured at the solder points, or the width of the component?


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## tangent

Quote:


  Originally Posted by *gsteinb88* 
_That thing has its back riveted on_

 

I don't think so. I think those rivets you're seeing are just for the signal pins. If you pry those four tabs back, the PCB should come away from the pot body, exposing the resistive track.


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## gsteinb88

I could be mistaken, but the rivets are attatched to the bottom of the piece held by the tabs. I.e. its one contigous piece. If you bend it back too far, its just going to snap, which wont be good.
 -g


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## lini

Looks quite similar to the one in the HeadBox MkII (compare this: http://www.m161fhr.pwp.blueyonder.co...ture%20003.jpg), so I'd assume that one should even be able to get a drop-in replacement with a bit of searching...

 Denim: Have you already tried calling up or emailing the Yamaha service? They should be able to at least tell you or maybe even sell you what you need.

 Greetings from Hannover!

 Manfred / lini


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## PinkFloyd

Cheap as chips carbon 100K dual log pot, whip her out and replace, you can pick these pots up for under a quid at most electronics suppliers.







www.rswww.com part number 249-9288 (50K log, will be fine I think) Just establish whether the pot shaft is splined or not. If there's no grub screw holding the knob on it's probably not a splined shaft, pull the knob off to confirm.


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## mono

Quote:


  Originally Posted by *gsteinb88* 
_I could be mistaken, but the rivets are attatched to the bottom of the piece held by the tabs. I.e. its one contigous piece. If you bend it back too far, its just going to snap, which wont be good.
 -g_

 

There are 6 rivets. Each rivet holds one contact, pin, at the bottom, 3 contacts x 2 boards. They are not to be bent, it is very important not to bend this area because the rivet is the mechanical-electrical junction between each of the 6 pins and the carbon tracks on the boards (in the pot, not the daughterboard the whole pot is soldered to).

 To open the pot, the 8 metal tabs that are same piece as the metal body of the pot are bent upwards. It would be easier to see this if you had the pot in your hand but these are those tabs,







 When I'd mentioned rivets previously, I was referring to some pots that have a molded plastic or metal, square body, and plastic or metal end-caps. With those types, typically there are rivets holding the front and back on instead of bent tabs. A loosely similar method of construction has a plastic body with studs molded into it, and after the end caps are put on the body the studs stick through holes in the end caps and a machine that might be a bit like a plastic welder melts the protruding ends of the studs down to form rivet-like permanence. With any of these, opening the pot is easy with precision drilling but putting the pot back together again requires an alternate fastening system in many cases. Not all are like this, fortunately some have screws instead but those are inherantly larger and more expensive pots.


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## PinkFloyd

I've got quite a few of these old pots kicking about shall I strip this one down and show you the guts?


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## Denim

I removed the pot at work today and metered it out. It is a 0 - 100K ohm pot (center to outer pin). The shaft is about 3/4" long, and notched (for lack of the correct term). The pic that PinkFloyd posted is an extremly close match.

 Hope to place the order this evening. Thanks for the input guys.


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## PinkFloyd

Well, just in case anyone else wants to clean one at any time I took a pic.... your best friend here is a pair of long nose pliers, just pull up two of the tabs on the rear casing and pop the track out as shown. The front is exactly the same but you'll have to pull all four of the tabs up. Clean, replace and pop the tabs back into place using the same long nose pliers. Takes about 5 minutes.


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## PinkFloyd

Quote:


  Originally Posted by *Denim* 
_I removed the pot at work today and metered it out. It is a 0 - 100K ohm pot (center to outer pin). The shaft is about 3/4" long, and notched (for lack of the correct term). The pic that PinkFloyd posted is an extremly close match.

 Hope to place the order this evening. Thanks for the input guys._

 

The shaft you're looking for is called "splined" you'll have no difficulty sourcing one they're pretty generic. You don't have to go with a 100K and 50K would be fine if you can't source 100K. Just be sure to ascertain if the pot is linear or logarythmic. It's definitely a dual gang type being it has 6 pins and is most probably a log type. 

 Good luck and if you need any help just ask, we're here to help.


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## Denim

It is a log type as you expected. The pins are 5mm apart, I hope that's on a data sheet, or typical. The shaft is about .8" long and .233" dia. 

 What wattage rating are these, .5W? 

 I'll begin the search after dinner.


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## Denim

Quote:


  Originally Posted by *lini* 
_Denim: Have you already tried calling up or emailing the Yamaha service? They should be able to at least tell you or maybe even sell you what you need.
 Manfred / lini_

 

Why didn't I think of that? They have a service center about 45 miles away. I'll call them tomorrow and see what they have. With luck, they will point me to a replacement through a local electronics house.

 I'm obviously going to have to learn to search better if I ever want to build a headphone amp.


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## PinkFloyd

Quote:


  Originally Posted by *Denim* 
_
 I'm obviously going to have to learn to search better if I ever want to build a headphone amp. 
	

	
	
		
		

		
		
	


	


_

 

I'll find you one later, what part of the world are you in?


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## Denim

Quote:


  Originally Posted by *PinkFloyd* 
_I'll find you one later, what part of the world are you in?_

 

I'm in Lakeland, Florida (USA, 33809 zip). I've gone through Digikey a few times, but came up empty. I believe I want through-hole, panel mount, 100K, carbon. After that, it gets confusing. I couldn't filter on all 4 to narrow the list down. The shaft turns about 300 degrees. 

 Thanks for helping me out, PinkFloyd!


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## Denim

Yamaha no longer carries the pot and they don't know the original source and part number. The Yamaha part number is HS311890. Google found a German message board with a guy looking for a replacement also. That was a couple years ago.


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## PinkFloyd

Quote:


  Originally Posted by *PinkFloyd* 
_Cheap as chips carbon 100K dual log pot, whip her out and replace, you can pick these pots up for under a quid at most electronics suppliers.






www.rswww.com part number 249-9288 (50K log, will be fine I think) Just establish whether the pot shaft is splined or not. If there's no grub screw holding the knob on it's probably not a splined shaft, pull the knob off to confirm._

 

I'd just go with the one above (the 50K one) not a splined shaft but you can fit a nice new knob with a grub screw fixing onto this pot pt no: 249-9288 www.rswww.com I'll have a rummage around tomorrow and see if I have a splined shaft one kicking around for you, doubt it but you never know.


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## Denim

Thanks for the part number PinkFloyd. I followed the link and ALPS has a 100K variety that should fit. I haven't found a dealer in the US that has that item yet, but I might have better luck tomorrow.

 I called Digikey and they don't have any through-hole pots. The guy knew what I was looking for and the smallest thing he had was a 2W size. Searching for ALPS brought me to Mouser. They didn't have the part listed on-line, but I think they may have a suitable pot. I'll call them tomorrow when they are open and see what they have. 

 I have stayed away from Radio Shack, I'd hate to put a Radio Shack part in my amp. How much influance, if any, will the quality of this part affect the overall sound of the amp?


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## mono

Quote:


  Originally Posted by *Denim* 
_Thanks for the part number PinkFloyd. I followed the link and ALPS has a 100K variety that should fit. I haven't found a dealer in the US that has that item yet, but I might have better luck tomorrow.

 I called Digikey and they don't have any through-hole pots. The guy knew what I was looking for and the smallest thing he had was a 2W size. Searching for ALPS brought me to Mouser. They didn't have the part listed on-line, but I think they may have a suitable pot. I'll call them tomorrow when they are open and see what they have. 

 I have stayed away from Radio Shack, I'd hate to put a Radio Shack part in my amp. How much influance, if any, will the quality of this part affect the overall sound of the amp?_

 

The original pot was low quality taken from a audiophile perspective, as are most carbon pots. To a certain extent, it might be splitting hairs calling one from Radio Shack lower quality than one that looks about the same but sold elsewhere. FWIW, at some point the 'Shack was selling an Alps of that type but I don't recall the value.

 When considering these low-end pots, you'd be concerned a lot about tracking. Suppose it has 20% tolerance, you don't want your L & R channels off by 20%, IMO. 5% maybe, 10% maybe but it matters a lot whether your preferred listening level just happened to coincide with where the two weren't in sync. If you find a place that has what you want and it's a similar looking pot to what you had and not spec'd for low % tolerance, you might consider buying at least 2 or 3 pots then pick the best of the lot to use.

 You might measure the hole this pot mounts in and see what else would fit. If you were going to be listening to this amp (and adjusting volume) a lot, it might be worth a few bucks more for a better pot. Tangent sells an Alps 50K that's nice, but I don't know if the pins would match your pot daughterboard. It doesn't really need to match though, you should be able to look at the board and wires, and wire direct to the pot pins. If the leads are too short for that it becomes more involved to pull out (or maybe it's in some sort of socket) the ribbon cable and put in an longer cable or separate wires.

 If the pot won't fit through the hole and you're really ambitious you could even enlarge the hole, but then there's the volume knob size to consider too.


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## Denim

I have some room to play with. The pot is mounted on a seperate card that has a ribbon cable running to the main board. I don't need a through-hole style, as long as I can route the wires to the correct place on the card. 

 Good suggestion about metering the pot. I didn't realize until now that the left and right channels are handled seperately within the pot. It suddenly makes more sence! I'll take at look at what Tangent has.


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## Denim

I ordered a pot from Mouser at lunchtime today. Not an exact size match, but it should work. Hope to have it Monday or Tuesday. Their part number is 313-1240F-100K.
 Thanks for the help, I was a bit lost for a while.


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