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Restoring my 3's


DavidDru

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So here i go, diving into restoring the AR 3's that I had previously posted about finding a couple months ago. I am basically a newbie at this so I will be relying on all the help you guys have the time to offer. So you know, I am not doing this to flip them and I plan on having these as part as my main vitage system in my very cool mid century lounge. Within that lounge will be a high power solid state system featuring the AR 3's and a tube system (Dynaco st70) with either Heresy's or Altec valencias.

As previously described in my initial thread about finding these, I got them out of a basement of an old dilapidated warehouse building and got them cheap. Finagling with the pots I was able to get sound out of each driver but not enough to be confident of how well they will work. the cabs are not too bad and are the least of my challenges until I know they are working. JKent has already helped with some options for Grille material and badges for the finishing touches. Thanks J Kent!

As I go I hope you guys feel comfortable chiming in on things you see in my posts that I should be doing or considering. This is fun stuff so lets have at it. I can use all the help I can get! Of course, teh AR3a restoration guide will be my tool and guide for the work. Since the 3's a re a little different let me know where and when as we go please.

Thus far I have removed the grilles, the woofer driver and the insulation. I carefully vacuumed out the insulation and dust particles and the attached photos is what I have. Oh BTW, we are dealing with Schematic C. Of course I started another thread the other day regarding the pots. These feel really bad and considering I was barely ever able to get sound through them they are probably pretty bad. With the insulation and woofer out, I think I will go there next to see what I have to work with.

A question I have at this point is when you guys desolder the connections do you just you a solder wick or what?

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Many guys have success with wick but I'm not one of them I like the big blue plastic solder sucker like this one http://www.amazon.com/Orange-Plastic-Desoldering-Solder-Sucker/dp/B00G98ZE26/ref=sr_1_5?s=industrial&ie=UTF8&qid=1415855187&sr=1-5&keywords=solder+suckers

Suggest you take the pots apart, being careful because there "may" be springs in those early ones. Then post photos. They can often be restored.

The HK pots (Chinese knockoffs of Ohmites) that Roger linked to look like they may show promise but they will require enclosures (a PITA) and you will lose the "white dot" setting.

Which reminds me. Keep track of where each pot is installed because there is a dimple in the Masonite where they are installed. I never did that but it may be important for authenticity.

Or just install $5 L-pads and have no worries......

Good luck with that fantastic find!
Kent

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After reading all the efforts of others on this site it seems the challenge of replacing pots is one of the bigger obstacles one can face. That's kinda why I started that other thread. For it's own focus and so others don't have to navigate thru this one to look into that aspect alone.

Question. JKent chimed in on de-soldering above, but when you guys do these efforts, do you think it best once you de-solder the wires to go ahead and snip off all the old stripped ends and re-strip to create a new clean end? Or leave it to re-use. I am new to the soldering thing so I don't know if there is a reason either way I need to know about. Where I am going is it seems it would be easier to cut off all the wires in the cabinet and then de-solder one the piece are out on the items that will be going back in. Or is this what you mostly do already. Can you tell I am new to this or what.

J Kent, I had noted the various points related to the "white dot" and indentation within the guide and I believe some of your other posts so I have my radar on for that aspect. probably will make sense once I look for it.

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I've replaced/repaired pots on two sets of AR's and recapped two sets of crossovers. On those two sets I've found that the wiring to the pots were wound around the terminals and a lot of solder was applied. If I've had sufficient wire available I've ended up cutting the old stripped section off and re-stripping to start anew. In a couple of cases, I've completely replaced wiring that did not have sufficient length. Take your time, get yourself a good de-soldering bulb. Find an old component if possible and practice soldering and de-soldering. It's not all that difficult with some practice.

Best of luck to you.

der

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I went in and pulled the pots out of speaker 1 and this is what I got, before and after cleaning. To clean them I bathed them in vinegar and salt, scrubbed with tooth brush, used an electric eraser I use for drafting, and use some Neverdull metal cleaner and polish. Seems like the worst part are the two round rivet things at the beginning and end of the coil. The wipers look better than the reflecting pictures makes them seem.

I'll try to test them tomorrow unless you guys think I should try to be a little more aggressive with them first with my dremmel or something. Stupidhead, your pot cleaning exhibition post you linked to AK have given me hope! mine dont look as good as your best ones but better than your worst ones. The rivets scare me the most.

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I went in and pulled the pots out of speaker 1 and this is what I got, before and after cleaning. To clean them I bathed them in vinegar and salt, scrubbed with tooth brush, used an electric eraser I use for drafting, and use some Neverdull metal cleaner and polish. Seems like the worst part are the two round rivet things at the beginning and end of the coil. The wipers look better than the reflecting pictures makes them seem.

I'll try to test them tomorrow unless you guys think I should try to be a little more aggressive with them first with my dremmel or something. Stupidhead, your pot cleaning exhibition post you linked to AK have given me hope! mine dont look as good as your best ones but better than your worst ones. The rivets scare me the most.

Look at where the wiper makes contact with the disc. That area has to be smooth to work properly so scrubbing, grinding, buffing, sanding, etc. Need to get some deox solution into the rivets also, especially after using salt and vinegar. I would even drop them into boiling water with a pinch of baking soda.

Roger

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Hi David,

Now we are getting somewhere! I have certainly seen worse! As Roger suggested, maybe a bit more finishing is called for. I have recently accumulated another batch of pots for restoring and grading and came upon this set...

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which serve as good examples showing where the wiper contacts the disc. This pic is before any attempts to clean up by the way. One of yours (the cleaned up left pot) looks pretty crusty on that area from say 1:00 to 6:00 and maybe a little dremel with brass or soft steel brush may help.

Geoff

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David... nice find too. take your time and do not try to do everything once. This way your fun will last longer.

Salt and vinegar dip corroded lugs of my pots so much that oxidation had to be removed mechanically from lugs before regular lead/tin solder did adhere... and it did not do that too well after I was thinking lugs are clean enough. If there are no holes corroded in the wiper track I would use only tooth brush, toothpaste, 600-1200 grit paper and water. Deoxit will not make any harm. If this is not good enough I would use vinegar. I would add salt to vinegar only if there are major pits to be cleaned on track.

Only one AR2ax pot was bad enough to need slat and vinegar. This cleaned pits enough to be filled with silver solder, but oxidized lugs quite badly. Geoff your pots look like they need only mild cleaning... try this first and do not overdo as it might save time and provide better end results. I overdid, wasted time and results were not good.

Best Regards

Kimmo

PS as 2ax white dot settings of tweeter are quite different to squawker (did I spell this right way).... so, I used best track available near end of track for tweeters and best condition track close to middle for squawker... this idea may not suit 3´s too well, but might be usefull somewhere else too

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So if I keep sanding/grinding, will I get back down to the clean metal?

I did the salt vinegar bath because there was a lot of the blue corrosion on the other side down in the recessed holes for the connectors where not too many tools can get. I was going to do it with lemon and salt but all I had was a lime so I had a margarita instead.

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There was only one lug with blue corrosion on back side (lug side) during my 2ax pot rebuild... which seemed odd. Maybe this was some kind of turn over to different materials batch of pots, since one wiper was made using different material or plating.

Best Regards

Kimmo

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I went at them a little more with a dremmel and a couple different tips. Most of the pitting is gone, but not perfect. Not sure if the rest of the pot is in good enough condition to do all this work and then re use? I'll try to measure them next to see what I got. Apparently I might need another pair of hands since I don't have alligator clip leads. What two posts do you use with which lead? Do I want to put the grease in to take the readings or does it matter?

Here is also the woofer from this first speaker. Resistance reading seems fine coming in around the 3.5 range depending on exactly where I touch the leads to the post. Or does it need to read a constant steady 3.4?

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It is hard to tell how long time pots will work. If original plating of wiper track is good, where wiper is resting, pot will most likely work like new one. If wiper is resting on bare copper, pot is not going to be too long living. If you do not get reading from clean pot without grease, I would not use the pot. I figured that best time to do grease job is after soldering wires to lugs, so grease will stay little longer where it is supposed to be... but this is not easy to do in the cab.

Quality of DVM or tips of test leads are mos likely cause for fluctuating resistance reading of woofer. My autoranging Wavetek DVM has never given constant results... it seems that it can never decide what is correct last digit. However my el Cheapo LCR meter with hand selected ranges will give pretty constant readings. Better quality autoranging Flukes seems to give constant readings too.

Best Regards

Kimmo

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I am looking into what I need to replace my crossover on my MG IIa's over on the mug site and over there it has been suggested I replace the wire coil inductors with foil inductors. Is this not something done here on AR's? Just curious if there is a specific reason etc.

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Everybody seems to have their favorite inductor. Air cored inductors do not introduce core distortion, but wire lenght can be be many times more than in cored inductor... why use 30 meters of cabling between amp and speaker if only 7 meters are needed when using cored inductor. Core distortion is not too big issue if sensible sized cores are used.

Round, hex and foil has been used for coil winding. For given core, inductance and DCR... I suppose least amount of copper used is the winner.

One thing is certain with any core design... closely wound and varnish impregnated coils are the best.

Best Regards

Kimmo

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I am looking into what I need to replace my crossover on my MG IIa's over on the mug site and over there it has been suggested I replace the wire coil inductors with foil inductors. Is this not something done here on AR's? Just curious if there is a specific reason etc.

Save your money, David. There is absolutely no benefit in this. In fact, if the resistance of the original inductors is not taken into account you will likely change things for the worse. The dcr, not just the inductance, of inductors is part of the crossover design.

Roy

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Save your money, David. There is absolutely no benefit in this. In fact, if the resistance of the original inductors is not taken into account you will likely change things for the worse. The dcr, not just the inductance, of inductors is part of the crossover design.

Roy

Thanks Roy. I will have to dig a little deeper over on the MUG site on why this is recommended with the Magneplanar crossover. Doing it there is going to be expensive.

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if the resistance of the original inductors is not taken into account you will likely change things for the worse. The dcr, not just the inductance, of inductors is part of the crossover design.

Roy

When there is less than 30% power decrease after tuning or "hot rodding" engine, tuning can be considered successful. Peoples tend to think positively. If there is change... optimistic peoples do most often think that the change is in the right direction.

Best Regards

Kimmo

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  • 2 weeks later...

As far as caps go, any particular brands that you guys have not been pleased with that I should steer clear of? Also, with Erse, they have their two styles - polypropylene and polyester. Is one more suited than the other?

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When there is less than 30% power decrease after tuning or "hot rodding" engine, tuning can be considered successful. Peoples tend to think positively. If there is change... optimistic peoples do most often think that the change is in the right direction.

Best Regards

Kimmo

This has little to do with hot rodding, and more to do with re-designing a successful design by someone who has no qualifications to do so. You can easily measure the results of hot rodding a car, but golden eared opinions regarding speaker modifications are still just opinions. Few, if any, of these folks can offer proof of alleged "improvements" due to modifications of this type.

By decreasing the dcr of the inductor by using a copper foil version, you change the intended padding effects of the inductor and change the crossover point. This is the reason inductors of a specific gauge wire, and associated dcr, are used in the first place. It is as much part of the design as anything else.

Roy

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So I tested the first pair of the pots and the numbers are good. Kinda surprising. They still feel rough to the touch as I turn the knob but the numbers increase and decrease as they should. Is the concern that there might be blank spots along the way that I should be worried about?

Also, any thoughts on this sealant?

http://www.ebay.com/itm/FRESH-LARGE-6-OZ-PACKAGE-OF-A-R-ACOUSTIC-RESEARCH-SPEAKER-CABINET-SEALER/111514649859?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D27538%26meid%3Db1de6fa152dd442a86d8a3d24f117a36%26pid%3D100005%26prg%3D11353%26rk%3D4%26rkt%3D6%26sd%3D191421132110&rt=nc

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So I tested the first pair of the pots and the numbers are good. Kinda surprising. They still feel rough to the touch as I turn the knob but the numbers increase and decrease as they should. Is the concern that there might be blank spots along the way that I should be worried about?

Also, any thoughts on this sealant?

http://www.ebay.com/itm/FRESH-LARGE-6-OZ-PACKAGE-OF-A-R-ACOUSTIC-RESEARCH-SPEAKER-CABINET-SEALER/111514649859?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D27538%26meid%3Db1de6fa152dd442a86d8a3d24f117a36%26pid%3D100005%26prg%3D11353%26rk%3D4%26rkt%3D6%26sd%3D191421132110&rt=nc

The original pots didn't have any kind of protection on them that I could tell. Seems like the CAIG product line is fairly popular among restorers in general.

My concern was using a penetrating protectant to get under the rivets and prevent further oxidation there and using something that wouldn't dry-out or gum up in a few years.

The auction link looks like automotive panel sealer but you can also use the gray duct seal at your local box store. Roy prefers the speaker foam from Parts Express I believe. I have some duct seal but used some weather stripping foam as I was planning on taking them apart again soon and didn't want to deal with the duct seal.

Roger

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Thanks Roger. JKent chimed in as well and said that stuff is indeed just repackaged duct sealant from home depot. If it is indeed the same material that AR originally used, I guess that we be okay, but who knows for sure? Mine was still surprisingly pliable when I took the woofer driver out. I just ordered some of that foam tape Roy called out from PE to use. I have 3 pairs of Acoustic Suspension speakers to do so it should get me through all 3.

Sounds like a good idea spraying the deoxit type stuff. I'll do that and then a little of the dielectric grease I guess. Also, I was able to find a little couple oz tube of that stuff at Napa auto parts. I got some alligator jumpers to use with my meter leads so I can see how consistent the range is on the pots.

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I think AR and others originally used Mortite but the duct seal is probably better. PE sells nice ready-formed strings of the stuff and I use that sometimes but really prefer PE's self-adhesive foam gasket.

Kent

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... I'll do that and then a little of the dielectric grease I guess. Also, I was able to find a little couple oz tube of that stuff at Napa auto parts.

I'm not big on using that on moving parts. It does stiffen with age and it may cause the wiper to float. I have some that has been open to the elements for several years. I used some of it today on a waterlogged AC plug but I wouldn't use it on a pot at this point in time as it is definitely too thick.

Roger

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  • 1 month later...

Update. Back on the 3's now. Had to work on my amp for a while.

I took out the old cap in speaker 1 and the two values measured at 8 and 39 (supposed to be 6 and 24). Picked up another cleaned up pair of pots on the bay but they are no better than mine which are testing fine anyway. I am going to first re-attach everything in a temporary manner to see what I get out of the drivers that with the old pots were pretty much choked off. Need now to look at everyones examples of their crossover re-builds.

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