AR-2A Pots - Replace, Clean, or Bypass?

[dvdan1]

Hello, I recently inherited a pair of AR-2As of early vintage (or so I am told). It's fairly obvious the pots are bad; I can hear them grind when they are turned. When I opened the speakers up (yikes), I was surprised to find very large oil-filled caps in them. I must admit I didn't know what they were until other AR-2A AK members filled me in. And, I could see there was corrosion on the pots. So now that they're open, I have to make a decision: Clean, replace of bypass the pots? An eBay seller has highly suggested that I completely replace them because I'll just have the same problem down the road. The only problem I could see with that is, maybe they won't sound like they were originally supposed to, or that their value is decreased (yes, I plan to use the speakers, but I may just want to sell them down the road to make room for another project, or not). Another opinion was to just bypass them completely and use the treble and base controls on my receiver to control the tone instead.

I'm interested if any knowledgeable members have any advice for me. I'm also interested if anyone has a best practice for removing the pots. I'd like to remove the pots and the board they are attached to for easier soldering (not my favorite thing to do). Someone suggested carefully prying the board up, but there are many staples that connect it to the speaker cabinet, and I'm not sure of the best method to reattach it.

Thanks in advance. AK is the best!

 

[spark1]

First, you don't need to remove the board to remove the pots. Simply unscrew the external nut on the shaft. However, to remove them completely you will need to disconnect them. But, you can usually do a pretty good job of cleaning them without disconnecting them...a bit awkward, but doable. A dremel type tool with a brass brush will work well. Blow them out afterwards, and put a thin layer of dielectric grease on the resistive element.

There is little reason not to try and clean them before considering replacement. They can often be brought back to 100% operation, or close to it. Here is a very detailed thread about one approach to cleaning them:

http://audiokarma.org/forums/index....storation-guide-very-long-with-photos.306818/

If you decide to replace them, you can buy new pots of the same resistance, but I think the only ones available are open-backed and therefore you will need to rig up some sort of covers to keep dust/dirt/stuffing material out of them.

Alternatively, you can use L-pads (available with closed cases, and at a much lower price). In this case, you will lose the lower "half" of the range of the existing pots. For most people, this is not an issue...few AR2a users turn the pots below their center position. Most folks turn them "up" (that is, to a position of higher output...which of course is lower resistance).

As regards maintaining value for a future sale...if you are concerned about this, keep the original pots and put them back in before selling (or include them for the buyer to do with as he/she chooses). Neither new pots nor L-pads require any physical modifications to the cabinet.

 

[ra.ra]

Congrats on your "new" AR-2a's! It is not unusual to find the oil caps in the 2A model, and it is very probable that they will not require replacement. The original pots are notorious for developing corrosion, and the only way you'll be able to make an informed decision is to take them apart and inspect them closely. The pots may be worth restoring if having all original parts is important to you, but if not, 8-ohm 15-watt L-pads with 3/8" shaft make a very suitable and affordable substitution.

 

[dvdan1]

Congrats on your "new" AR-2a's! It is not unusual to find the oil caps in the 2A model, and it is very probable that they will not require replacement. The original pots are notorious for developing corrosion, and the only way you'll be able to make an informed decision is to take them apart and inspect them closely. The pots may be worth restoring if having all original parts is important to you, but if not, 8-ohm 15-watt L-pads with 3/8" shaft make a very suitable and affordable substitution.

Thanks! Just curious - Have you ever heard of anybody bypassing the pots completely?

 

[dvdan1]

First, you don't need to remove the board to remove the pots. Simply unscrew the external nut on the shaft. However, to remove them completely you will need to disconnect them. But, you can usually do a pretty good job of cleaning them without disconnecting them...a bit awkward, but doable. A dremel type tool with a brass brush will work well. Blow them out afterwards, and put a thin layer of dielectric grease on the resistive element.

There is little reason not to try and clean them before considering replacement. They can often be brought back to 100% operation, or close to it. Here is a very detailed thread about one approach to cleaning them:

http://audiokarma.org/forums/index....storation-guide-very-long-with-photos.306818/

If you decide to replace them, you can buy new pots of the same resistance, but I think the only ones available are open-backed and therefore you will need to rig up some sort of covers to keep dust/dirt/stuffing material out of them.

Alternatively, you can use L-pads (available with closed cases, and at a much lower price). In this case, you will lose the lower "half" of the range of the existing pots. For most people, this is not an issue...few AR2a users turn the pots below their center position. Most folks turn them "up" (that is, to a position of higher output...which of course is lower resistance).

As regards maintaining value for a future sale...if you are concerned about this, keep the original pots and put them back in before selling (or include them for the buyer to do with as he/she chooses). Neither new pots nor L-pads require any physical modifications to the cabinet.

Thanks for the great info. Anything that requires less disassembly makes me happy. I do have a Dremel tool, I'll just have to see if I have a brass brush in my collection. Looking forward to getting at it this weekend. I'll post updates as the project moves along.

 

[ra.ra]

Have you ever heard of anybody bypassing the pots completely?

There are people who do this, but I'm not sure exactly how to do it, and would not want that for my AR speakers. What I do know is that it is desirable to have functioning level controls to be able to suit the speakers to a variety of listening preferences and room environments.

 

[dzkfraser]

Cleaning the pots is not difficult - removing them from the cabinet and reinstalling them is probably the hardest part,(if you don't remove the board) the wires are soldered and desoldering them can be a royal pain - best to clip the wires to remove and desolder the wires left on the connections. Clean with vinegar and salt solution - I also use TarnX for some rough spots - lube with dielectric grease

 

[dvdan1]

Okay, so I finally had the chance to get the pots out. The first thing I noticed was, obviously, there are two pots in each speaker as opposed to some of the other AR speakers that are referenced in some threads. Secondly, the pots are different than some of the other ones referenced also. If they come apart for cleaning, it isn't readily apparent how they are disassembled. Anybody have any experience with these types? Photos are included. Thanks.

 

[RxDx]

Okay, so I finally had the chance to get the pots out. The first thing I noticed was, obviously, there are two pots in each speaker as opposed to some of the other AR speakers that are referenced in some threads. Secondly, the pots are different than some of the other ones referenced also. If they come apart for cleaning, it isn't readily apparent how they are disassembled. Anybody have any experience with these types? Photos are included. Thanks.

Yes, I've seen these. Internally, they're quite similar to the ones with the wire retainers.
These require you to bend the side tabs outward, which will release the halves. Then
carry on as usual.

 

[dvdan1]

Yes, I've seen these. Internally, they're quite similar to the ones with the wire retainers.
These require you to bend the side tabs outward, which will release the halves. Then
carry on as usual.

That did the trick. They're now taking a salt/vinegar bath as I type. Thanks. Getting them back together correctly might be a little more difficult.

 

[Go Giants]

Every pair of AR 2's 3's and 4's all had issues. To me, these adjustments were not really necessary...certainly not made to be trouble free after decades.

I had my 'speaker guy' bypass them on a pair of 4ax's. I sold my 3's...bad pots and all. The buyer was going to rehab anyway. Just bought a pair of 2a's today...same issue. I'll try to clean them, but if that doesn't work ill ask my guy to bypass them.

To me, these are just a pita. Especially on AR's and Dynaco's. I've had much better luck with KLH's.

 

[HamboneF18]

You’ll need those pots, or replace them with new ones. You’ll mess up the crossover points without them. I didn’t have to replace mine, they were clean and not corroded. But I bought 20 ohm/25 watt replacements just in case, before I opened up my 1965 speakers (2ax). The 20 ohm gives you just a bit more volume on the tweeter. That’s because AR used these as voltage dividers; higher resistance pots sends more current to the tweeter and midrange, because it shorts less current.

Originally wired like this:



My pots were like factory new:












Bypassing the pots changes the resistance seen by the crossover caps, so your crossover points will change some, and also removes some protection of your tweeters and midranges. Oh, and that gritty feel is supposed to be there; they are wire-wound rheostats, not plastic film potentiometers.

These are the ones I bought and tried out:




Mine, before I had done anything to them (left speaker fed a mono signal):

After replacing caps, inspecting pots, and my 2nd rebuild of the tweeters:

 

[Go Giants]

Okay, so I finally had the chance to get the pots out. The first thing I noticed was, obviously, there are two pots in each speaker as opposed to some of the other AR speakers that are referenced in some threads. Secondly, the pots are different than some of the other ones referenced also. If they come apart for cleaning, it isn't readily apparent how they are disassembled. Anybody have any experience with these types? Photos are included. Thanks.
View attachment 1250980 View attachment 1250981

Sometimes I've had luck just shooting come CRC into the little rectangular windows...without taking them apart.

This is the "quick and dirty" way to perhaps breathe life into the pots. Not a true repair job, but for someone like me...not very skilled...it can work.

If you try this, don't forget to work the CRC in, by rotating the two controls 30 or 40 times.