Is this AR tone control/pot any good?

stupidhead

aka Ratdogheads
Subscriber
Hello folks,

I have been enjoying my journey back into vintage audio, and with the assistance and guidance from many on this forum and others like it has been extremely helpful in this endeavor. My story is not unlike many I have read here in the intro forum, and if interested you can read mine here http://www.audiokarma.org/forums/showthread.php?t=556669

With that said, I have always enjoyed AR speakers, and have been accumulating various sets of vintage ARs to refurbish and enjoy. It all started with a set of AR 4ax' and the process of bringing them back to life can be found here http://www.audiokarma.org/forums/showthread.php?t=568900 which was a blast and I still enjoy these on an almost daily basis. It was also a great launching point to move forward and delve into more involved refurbs, and the input from forum members was invaluable. I now have two sets of AR 2x (one with cloth and one with foam surrounds), a set of AR 5s and recently Karma has another set of 4ax coming my way as well. This past Summer has been very busy here at the homestead and has not left much time for speaker work, but with Winter closing in, I can see a good deal of time available to move forward....finally.

Earlier this year I saw a posting on the auction site for a lot of 8 AR potentiometers and immediately moved on them. I believe I paid $50 for them and figured if I got 2 or 3 good ones I was doing OK seeing as they sell regularly for $20ish apiece. Here is a picture of what I received

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And I was encouraged, but recalling my 4ax refurb, I knew this didn't really tell the tale so I opened them up and here is the real tale

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and here is a closeup of a couple of the guts :tears:

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During my initial time in the forums, I had come across this thread http://www.audiokarma.org/forums/showthread.php?t=306818 which helped tremendously in what to do next!

Soak those babies. Wipers not visible but they are in there.

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and while they were soaking it gave me an opportunity to :smoke: clean up the other various parts of the assembly.

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and no I didn't use the dremel on the plastic red stems, :nono: they were just wiped with some soapy water and looked fine!

So after soaking for about an hour, a thorough rinsing in clear water and then some polishing with the dremel equipped with a soft steel brush attachment and voila..

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which reveals at least five combinations of usable sets! :yes: I am very encouraged. The last pic of the wipers clearly shows the two on the right to be degraded to the point of useless, and the third from right suspect at least. It is noteworthy to point out the difference in the mounting holes on the wipers being slightly different, and this will be important when putting these back together.

Well, it is time to get ready for work so I will finish this later tonight.:thmbsp:
 

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In the last pic, the 3-4 on the upper left look like they may be ok. The key is the condition of the contact disk. The smoother, the better. The pots in my 3's were bad and all needed replacement. Took a bunch to get 4 good ones. Roy C. was gracious enough to send me two in very good condition.

Close up pics of yours of the discs will be helpful for us to see their condition. I've read some guys flow solder on the surfaces when badly pitted, and file- polish them smooth to restore the disc surface.

Glenn
 
If the rest of the control is good maybe a machine shop could stamp out a rough wiper and you could finish it. They are not compound shaped. The key of course is the spring quality of the material. The wiper dimple could even be slightly moved to rub against a different section of the wire.

I am surprised we have not seen oe replacements coming out of China or someone assembling a stepped replacement using 1% resistors. Even a 10-12 stepper should suffice. For those who golf with Bill Gates maybe a 48 stepper.
 
miserable photo

In the last pic, the 3-4 on the upper left look like they may be ok. The key is the condition of the contact disk. The smoother, the better. The pots in my 3's were bad and all needed replacement. Took a bunch to get 4 good ones. Roy C. was gracious enough to send me two in very good condition.

Close up pics of yours of the discs will be helpful for us to see their condition. I've read some guys flow solder on the surfaces when badly pitted, and file- polish them smooth to restore the disc surface.

Glenn

Hi Glenn,

I will review my pics to see if I captured anything better. I didn't realize the settings were off when those shots were taken and the result was terrible. If I can id a better shot I will post. In the meantime, I have greased them and re-assembled the ones that I felt were worthy. Two of the wipers were NFG but I like the idea of flowing a little solder on the surface of the disc. I have a total of 14 more within the project speakers and hopefully I will end up with enough in total to not have to source any more!

Geoff
 
so I reviewed what other pics I had, and this is as good as it is going to get for a view of the "good" discs.

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The bottom right is probably the worst I think for the divot out of the right side contact rivet. Sort of wonder how that happened? I suspect maybe the wiper was left at that spot for a very long time or something. Maybe somebody can lend some insight.

Moving forward, the next step is to de-solder the terminals to prepare for install and new wiring to be soldered in place. I only did the five "good" ones and the solder sucker got a work out as evidenced from the scrap pile upper left.

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and adding this view just because I like the picture. :rolleyes:

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and now all that is left is to grease up the contact points

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and put them back together. Don't forget to put the larger pin on the red stem in the larger hole on the wiper!

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So all in all I am happy with the results. 5 what I believe to be usable original pots for $50 and a few hours of my time. Material costs minimal.

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:tresbon:
 

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Fingers crossed that you will get yourself at least a working quad of these. Exactly what did you find undesirable about the other pots - - - metal disc or the sweeper?
 
Hi ra.ra. found this on csp

"Good to hear that at least you tested the pots before re-installing them. I, too, use a combination of chemical and mechanical processes when trying to freshen up these crusty old pots, but you really can never anticipate their performance until you test the full sweep with a meter. And sometimes, the metal on these pots is just too far gone and they cannot be resuscitated, and must be pronounced DOA."

Can you explain the testing procedure please. I have a Fluke 115 but am not very skilled or knowledgeable in it's use. The observations about good or bad are strictly visual, and surface appearance on wipers and discs. To actually check with a meter would be very helpful and revealing. I am fairly confident that the two sweepers with holes instead of the raised button are NFG, are they salvageable?
 
Here's a pic of one of the Pots Roy sent me.
The pots that didn't pass and had to be replaced.


These two were sent by another AKer and cleaned up nicely and work great.
 
I think I briefly described the test process here in posts 45 and 47:

http://www.audiokarma.org/forums/showthread.php?t=609734&page=4

After you get the pot cleaned up, re-assemble the parts, hook up the meter and probes, and turn the control knob for variable readings. Ideally, you get smooth transitional readings from near zero to near 16 ohms. I usually do this in "dry" mode, and if it performs adequately, open it back up, apply the dielectric coating (silicone and/or grease), re-assemble once more and you're good-to-go.

The sweeper tips with holes are obviously pretty worn, but I did once resurrect one of these by creating more metal with a blob of solder to fill it in. So far, so good.
 
Thanx ra.ra

As a matter of fact I responded on that thread, my name is stupidhead after all! I will test and post my results.

Glenn thanx for the input, Roy is the man. We are lucky to have him around for sure! He has helped me on a couple of things as well.

Geoff
 
Thanx ra.ra

As a matter of fact I responded on that thread, my name is stupidhead after all! I will test and post my results.

Glenn thanx for the input, Roy is the man. We are lucky to have him around for sure! He has helped me on a couple of things as well.

Geoff
Hey, before you get to far along, use Dielectric grease on the windings. I did this and they operate more smoothly, the grease minimizes wear and also protects the contact surfaces from corrosion. Means much longer service life. Own AR3a speakers myself.
 
Well I am home and have tested the pots. All five read pretty much 0-16 with some slight variations!:thmbsp: I have no easy way to post pics since my meter only has probes which has led me to research accessories for it so I have ordered said "SureGrip Alligator Clips" which will arrive on Friday and then I won't need three hands to take pics so I will then take some and post them.:wave:
:wave:

Copa, check the fourth pic in post #5 of this thread. Not a great pic but I tried to show the grease on the windings there. A little dab will do ya. :D
 
Glad to hear that you're getting good readings, and I did notice the grease in your pic - - not only does it provide corrosion protection, but it lubricates the sweeping motion for a better feel. A couple of gator clips will be immensely helpful.
 
Well, the clips showed up today. :thmbsp:
Only one problem, I now realize I need the proper leads to adapt to the clips! Those are now ordered and will be here Tuesday. Pics then. In the meantime I have finished with one of the 2ax speakers, new Solen caps, two (of the five) refreshed pots, a very thin coat of the good stuff on the cloth woofer surround and a fresh thin snake of duct seal around the frame and done (for now). I have already worked the cab, but Mrs. Stupidhead still needs to work the grill cloth. Hooked it up in place of one of the 4x' and I am very encouraged. At first it seemed sort of harsh/raspy, but in about a half hour it smoothed out significantly. A little pot tweaking and it sounds real nice. Layla sounded real good at about 10:30 on the 2325 volume dial.:music:
 
final results!

and here it is Tuesday and my leads were here waiting for me. Amazon Prime baby!

Without further ado

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and the other side of the dial

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and what I have concluded is that all three remaining pots will serve me well for the next upcoming projects. They all seem to be able to be overspun if you force it. There is a definite change of feel to the dial when the contact leaves the spring surface and meets the lug.

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This is fun! :wave: :wave:
 

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