AR-3's needing TLC

[Finjima]

Hello, I occasionally visited these pages till now when I just acquired a pair of AR-3's. I like to restore the old stereos but i'm still a beginner seemingly. I have my work cut out for me with these AR-3's. Starting out they need new tweeters, someone had hacked in a pair of   H25TG-35 by Vifa and bypassed the rheostats and also rebuilt one of the cross overs. I have not taken out the stats yet to inspect them. also someone had doped up one of the surrounds so thick that coating to the surround needs to be removed and refinished. I might have a line on a set of AR-2a's and can salvage the tweeters there, but I won't know if I'm getting them till later this week. I also have to restore the cab's they have chips that need to be repaired and refinish the cabs. no grills... the mids work as well as the woofers, I came here to sort out my issues with this speaker and get a crossover plan in place for the rebuild.

here is crossover #1 with bypassed stats and hacked yellow wire (hooked to tweeter)

And Crossover #2 I will want to build the updated crossover for this set of speakers. 

see how thick this is on the outside edge, Inside edge is okish. only the one speaker has the cloth surround doped like this, the other woofer had the cap done but that looks ok.

From listening to these before tear down even as messed up as these I could see what the big deal was with these speakers, that mid is really sweet. 

I read the restoration guide for the AR3a (why isn't there one for the AR3? strange) so I know there is much that is universal that I can follow along with and its been a help so far. 

are there any AR-3 experts in florida? 

[JKent]

Welcome to CSP Finjima!

What a mess! Hop you can get the goo off. The ONLY sealant that should be used is RoyC's butyl toluene mixture.

I started to recommend reading the 3a document but I see you have! If you can get some AR-2/2a tweeters and remove the goo you should be in good shape. Hope the baffle wasn't butchered to get the Vifa tweets in there.

The AR-3 crossover is pretty simple and I see the inductors were left in place, so building a new one should be pretty easy. Here's a document from John O'Hanlon and Tom Tyson that should be helpful. When I worked on mine, one (SN 18051) had the #1 and #3 inductors but the other (SN 21651) had only the #1 0.4uH but not the #3, 0.04uH. I installed a Jantzen 0.o5uH, unwound down to 0.04. The project box encloses new Ohmite pots.

-Kent

AR-3_Crossover_Schematics_08July2008_OHanlon_Tyson.pdf

[stupidhead]

Kent, is there any conflict with the 2a tweet being 8 ohm vs. the 3 being a 4 ohm?

[Finjima]

After reading the this schematic I see i have the right one, I guess compared to the AR-3a crossovers I thought there was more to the AR-3's than there really was. Ok I'll need to choose caps then. whoever put the Vifa tweets in did not have to mod the cab to pit them in. thank god. now I'm off to pull the stats out, Ill take pics

[Finjima]

Ok for caps I can choose new films made by some of the popular brands known for their sonics and quality or I can go with the old russian PIO's for example. this is something i'll be mulling in the coming days

[JKent]

2 hours ago, stupidhead said:

Kent, is there any conflict with the 2a tweet being 8 ohm vs. the 3 being a 4 ohm?

ummmmmmmm...... ask Roy.

It's my understanding it's the same tweeter but what do I know?

[ra.ra]

Original AR literature seems to state that the drivers used as the AR-3 and 2a super-tweeter were identical.

[Finjima]

I just read last night on a reply post by RoyC where he said from talking with Allison who confirmed that there was only one tweeter between all the different models that used them regardless  if it was 4 ohm or 8 ohm speakers. I probably will not be able to retrieve the post because I read a lot of them last night regarding this. 

is the vineger/salt water treatment for cleaning the pots the best method? 

also on my Dynaco A25's there is a different kind of pot with just 5 resisters on it. would this be a valid option for these AR's? (just tossing around ideas for thought)

[JKent]

Vinegar/salt will work. Then clean thoroughly, make sure all is shiny, coat with dielectric grease. 2-3 year later repeat, and so on. Or use L-pads and forget it.

There are stepped attenuators being sold but I can't find a link right now.

-Kent

[ra.ra]

Yeah, with AR-3's, it's a good idea not straying too far from the original concept. If you are unable to get the original pots back into shape, new L-pads offer a good inexpensive replacement solution, or you could purchase more expensive Ohmite rheostats like JKent used in above pic (you'll need to read his thread for more info). 

I saw the pic of your pots in a different thread on another site, and they have developed significant oxidation build-up. That is not to say that they cannot be restored to again become functional, but that will depend mostly on the condition of the contact metal after you've attempted to clean them. Posting your pics in this thread might be very helpful in getting proper guidance and several good options. 

[Finjima]

ra.ra your right during my preliminary cleaning we had a casualty of one the the clip tabs broke during preliminary cleaning and inspection 

I'll post the rest after lunch

[JKent]

Go with L-pads and resistors. According to Roy, later ARs used L-pads and AP pots will just go bad again if if cleaned.

I'll also throw in my 2 cents on Ohmites: Waste of time & money. I bought some for $7 each from Skycraft years ago so I put them in my AR-3. They are not encased in any protective cover so I had to improvise something. Used a small project box but it was a PITA. AND I've been told (but cannot verify) that even Ohmites will corrode.

There are/were some Russian pots on ebay but they were also naked. The stepped rheostat looks like a lot of trouble. After all, the levels are usually a matter of set and forget. L-pads will work fine.

With respect to caps, you saw the Clarity caps in mine. So not worth it. Some restorers advocate using NPEs because their ESR is the same (presumably) as the originals'. Or use long-lasting film caps. Mylars such as Carli have ESRs closer to NPEs than do polys. You can also add a little resistor to the film cap to make it more like the original.

-Kent

[genek]

The inside of an L-pad has windings and a wiper, just like any rheostat (which is what L-pads and potentiometers are, just different types of rheostat). 20 or 30 years down the line, they'll probably be just as susceptible to corrosion.

[Finjima]

Will the Dynaco L-pad work in this crossover? or something like that where we can do steps?

[ra.ra]

2 hours ago, Finjima said:

we had a casualty of one the the clip tabs broke

Ouch! I've never had that happen, but after having looked at your corroded pots, I suppose that should not be surprising. Before you give up however, attempt a bit more cleaning to see if they just might be salvaged. You can always get another wiper from someone on this forum, if needed.

2 hours ago, JKent said:

Ohmites: Waste of time & money. They are not encased in any protective cover

I'd agree these Ohmites are overpriced, but I've never fully understood the desire for encasement. More than one version of early AR crossovers (see AR-2's attached) used rotary controls that were fully exposed to fiberglass or mineral wool cabinet stuffing, and I've never heard of them getting all clogged up with fibers. That said, I did once show on these pages a pair of A-P pots from some AR-4's where mineral fibers had gotten inside thru the vented openings.

23 minutes ago, Finjima said:

Will the Dynaco L-pad work in this crossover?

You can certainly create something similar that would work, but again, I'd strongly urge you not to stray too far from the original concept of components for operation, particularly with highly collectible AR-3's. Remember, you are trying to make improvements to the half-baked attempts you described and showed in your initial post. AR speaker models in the 70's used multi-step switching mechanisms for variable driver output, and the Dynaco system typically worked well, too, by varying the amount of resistance in the circuit, but neither of these is true to the concept of variable rotary control.

(Note: site is not allowing me to post 86KB jpg file - - - will try again later.)

[Finjima]

here is the pots cleaned up, only one tab survived

[RoyC]

Finjima,

The wipers are the least of your concerns. Those pots are nowhere near satisfactory. I toss them when they are in that condition.

Roy

[Finjima]

Ok tossed them. YOu think acetone would work on that one surround I posed about?

[RoyC]

22 minutes ago, Finjima said:

Ok tossed them. YOu think acetone would work on that one surround I posed about?

Unfortunately, there is no way to know unless you have some idea of what it was coated with. Be careful as you try different solvents. It is often easier to dissolve the glue holding the surround to the mounting ring than it is to remove the stuff on the roll. It appears someone really messed up that surround.

Roy

[genek]

I wonder if it might be better to dissolve the glue first, then try to remove the goop from the dismounted cloth surrounds.

[lakecat]

6 hours ago, RoyC said:

Unfortunately, there is no way to know unless you have some idea of what it was coated with. Be careful as you try different solvents. It is often easier to dissolve the glue holding the surround to the mounting ring than it is to remove the stuff on the roll. It appears someone really messed up that surround.

Roy

I told him on other site to use acetone with Q-tips on the area you describe Roy....and see if it removes any. It evaporates fast so little chance for damage. Only other chemical I would try is small amounts of lacquer thinner. 

 

[Finjima]

OK got a early start this morning and successfully cleaned that gunk off the surround. one thing I did notice is that the dampening ring is off center. ok Pics!!

It's what the Pro's use, 100% Gunk removing Power! 

Notice my work station also doubles as a laundering device for cloths

I think the guy who caked this stuff on thought of a rubber surround type finish was called for. (this is a after cleaning shot)

 

a wide angle shot of the surrounds and also see the off center mounting of the dampening ring. I hope this is OK and nothing to be concerned about. 

lil easier to see here

the cap looks like it isn't air tight (hard to see in these pictures) I think I need sealer.

 

[lakecat]

Quote

 

Great job!...glad it worked. I have never seen the ring off center but I can't imagine it being a negative. I would try to put that higher gap at top when installing it though.

 

[Finjima]

I was able to pick up the AR-2a's they came untested as-is at a local auction. I haven't tested them yet but first thing i did was take the grills off and kept  them on one piece. the mids are warped on both speakers and are no good, the woofers look ok but the small dampening ring are fragile and crumbly. so check out the tweets

I'll test these tomorrow as well as the pots

 

[Finjima]

ok good news all around, unless the readings I got off the tweeters arn't good, 1.7 ohms on 1 and 1.9 on the other, I took the readings with the tweeter disconected as shown in the pic . the Pots look great and should be keepers to use in the 3. th bad news those 2 things (tweets and pots) was the only good things from that speaker, on one of the woofers the masonite board the surround is mounted on is loose, the mids are toast too (I'm talking about the AR-2a i picked up last night) ok it ain't real unless there is pics so here we go

different kind internally than what is on the 3 I got. But I'll clean these up and roll with em

the voice inside my head was screaming STOP!! when I started to try prying these off, I recalled the busted up pair I been seeing on eBay and now I know how they got busted up now. Soooo HELP!!!!!      Also how do I get the wire off the terminal?