Acoustic Research Potentiometer Restoration Guide (VERY LONG, with photos)

Most 4x woofers do not need much, if any, re-sealant because most 4x cabinets are not meant to be airtight.

Good point, I'm wondering though about the lifespan of the cloth surrounds. I expect the surrounds to deteriorate over time like the grill cloth, and apart from improving the sound, is the sealant in part to protect the cloth, improving its longevity?
 
In a word, awesome. Nice work, and great contributions by others as well. I've restored one pair of AR3a speakers, so most of this will help those doing Vintage AR in general, of course with some exceptions.
 
Most 4x woofers do not need much, if any, re-sealant because most 4x cabinets are not meant to be airtight.

Good point, I'm wondering though about the lifespan of the cloth surrounds. I expect the surrounds to deteriorate over time like the grill cloth, and apart from improving the sound, is the sealant in part to protect the cloth, improving its longevity?

Perhaps, but I haven't seen that to be the case (yet). An application of the compound I mentioned above could serve that purpose. It can't hurt the surround and it is removable.

Roy
 
I finished the AR-4x's this weekend, and I'm pleased with what I have. I went through the pots and cleaned them up, then recapped, replaced the toxic fill, resealed and now they're going strong. Refinishing the cabinets will be the next step.

Thanks for all the input.
 
Went through the ol' guide and cleaned up some formatting and grammar. Did I really write this thing 3 and a half years ago?

"The Tmad AR Shop" is still going strong - our current project is to compare FOUR PAIRS of AR-3a's, keep our favorites, and sell the rest to worthy owners. Don't be surprised if some show up on AK soon... :)
 
AR4x Potentiometers: Scrap?

The wiper on at least one of my AR4x Pots has a hole corroded through the center... I'm thinking there is no way to fix it and the entire pot is now scrap, even though the restisor element appears in OK condition (other than surface corrosion). Anyone disagree?

See attached photos

Also... I could not find the restoration guide that tmad40Blue created... The link at the bottom of your post just keeps circling back!

btmacdou
 

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The wiper on at least one of my AR4x Pots has a hole corroded through the center... I'm thinking there is no way to fix it and the entire pot is now scrap, even though the restisor element appears in OK condition (other than surface corrosion). Anyone disagree?

See attached photos

Also... I could not find the restoration guide that tmad40Blue created... The link at the bottom of your post just keeps circling back!

btmacdou

btmacdou,

Yep... that pot looks like it's met its end. I would begin the search for a replacement - there are plenty of guys around with extra original pots. What's the other one look like? If it's in similar condition then it might be worth it to find and buy a pair.

Not sure what kind of trouble you're having viewing the guide - you're already in the thread. Click on the link at the bottom of my posts, and then scroll down - you will see the guide. Keep the Table of Contents page open to be able to quickly skip between different parts of the guide.
 
The wiper on at least one of my AR4x Pots has a hole corroded through the center... I'm thinking there is no way to fix it and the entire pot is now scrap, even though the restisor element appears in OK condition (other than surface corrosion). Anyone disagree?

See attached photos

Also... I could not find the restoration guide that tmad40Blue created... The link at the bottom of your post just keeps circling back!

btmacdou

You could put a small blob of solder over the hole for now. One of my wipers had been repaired that way, and a second one I did the same, and got pretty good readings on the meter. Just food for thought, until you find a replacement.
 
AR4x Pot Rebuild

Tmad40Blue... yes I found your guide this time thanks, and well done!

Regarding the idea of rebuilding the bulb on the end of the wiper... I had a similar idea to the solder blob, but I am thinking a good jewler could add a small bead of brass, bronze or even silver that could be filed and sanded to approximate the shape of the original.

I think this would be much better than solder which would wear away fairly quickly if the pot was used much. Yeah I know it should not be used that much but if I'm going to the trouble to rebuild it, I would like it to last another 40 years!

:)
 
Superb guide ! Unfortunately couldn't revive mine (Looked like someone put 1000v through them!) had to replace them with L-Pads from Vintage-AR. For what its worth, they function just the same & sound no different at all so don't despair if you can't fix yours people =)

Be careful with the L Pads. With the original rheostats, the resistance is still in parallel with the driver with the control set at max. With the L Pad, it becomes an open circuit and could overdrive the drivers, especially the tweeter. My AR-3A speakers had the rheostats replaced with L Pads by the previous owner. I discovered the open circuit situation when I rebuilt the crossovers, so added a 30 ohm, 12 watt resistor in parallel with the midrange and tweeter.

The quick fix is don't turn the L Pad to max. Turn it to maybe 10-20 degrees below max and there will still be parallel resistance.
 
Tmad40Blue... yes I found your guide this time thanks, and well done!

Regarding the idea of rebuilding the bulb on the end of the wiper... I had a similar idea to the solder blob, but I am thinking a good jewler could add a small bead of brass, bronze or even silver that could be filed and sanded to approximate the shape of the original.

I think this would be much better than solder which would wear away fairly quickly if the pot was used much. Yeah I know it should not be used that much but if I'm going to the trouble to rebuild it, I would like it to last another 40 years!

:)

I like the jeweler idea!

I know solder would wear more quickly, but how much would one really be turning it back and forth to wear it down to nothing?

So please post pics if you go the jeweler route.

Glenn
 
Repaired A4x Potentiometer wiper

Well.. my experiment at restoring an OEM AR4x potentiometer seems to be a sucess, other than cost (although I have not finished putting everything back together).

I took the wiper to a local jewler and he put a button of silver solder on the wiper. Photo attached.

The only down side is that he charged me $40 for the repair, and Vintage AR sells a new manufacture pot for $15.. hmm.:scratch2:

Anyway it was a fun experiment.

Here are after (Left) and before (right) photos:
Repaired_Wiper-M.jpg
AR4x%20Pot%20Wiper%20Damage-M.jpg
 
Just say NO to rockwool

Excellent tutorial tmad40blue! Saved me a big headache. The only difference on mine was the elimination of rockwool which I replaced with polyfill. Thanks
 
I'll spend some quality time with this thread this weekend. When I did my 3s, I didn't do the pots. I knew I'd go back in at some point and take care of them. Well, one mid pot has absolutely refused to work at all. It's fine if I hold it in, but this makes for a poor listening position. So I guess it's time to take them apart for what I hope will be the last time and get this taken care of. Thanks for the excellent write up!
 
Thanks sooo much to Tmad40 for the awesome walk through. Pots are now AOK and working good. Tomorrow I get some insulation...That rock wool crap sucks big time. My cabinet sealer seems ok believe it or not. Its still pliable and soft. Woolite test for the grill cloth tomorrow also. If that doesn't work I'll get new ones.

The only prob I had was that the wires after the pot refurb were so short coming from the cap and the ground(?)..Had to add some to the cap wire
 
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