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AR-2A Info


Audiophile03

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The pots should measure about 16 ohms, end to end. Vinegar is great for cleaning corrosion, if you haven't tried it before.

Various data points here.

Here's a schematic. Check your own speakers for variances.

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A worthwhile project! I really like the 2a. One suggestion: Check the caps. In mine they are apparently oil-filled military surplus (I'm guessing) and probably do not need to be replaced. A cheap LCR meter will confirm that.

Kent

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Hi

I am working on a pair as we speak. I am confused on cap values.

Pics attached of mine. I cannot seem to separate the two sets to see the values on the smaller ones. the top one says 2 mf, which is different from the schematic. Also, please share any comment on whether these need to be replaced. the mention of oil-filled military makes me wonder. I generally replace capacitors with good results. I was able to open the pots for cleaning. Hopefully these will free up.

Thanks, G

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Those are oil-filled. I'd leave them. If you poke around a bit there is probably another one in there as well. The bundles are wired in parallel to make up the 4 or 6uF value. Attached is a photo of the caps in mine.

Kent

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Those are oil-filled. I'd leave them. If you poke around a bit there is probably another one in there as well. The bundles are wired in parallel to make up the 4 or 6uF value. Attached is a photo of the caps in mine.

Kent

Thanks for the reply.

I don't see any other caps, but if these are still good, then they will stay.. I will clean these pots today. Now if I can just get these darn griil cloths back on in reasonble condition. Onward.

Glen

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dxho, I like the way you drew the schematic. It's closer to how I've redrawn it. The way many people draw schematics and wiring diagrams drives me nuts. I sometimes have to redraw them just to understand them. I also don't understand why the caps for the mid and tweeter aren't in series on the + side of the input and the speakers connected from the sliding contactor terminal 3 to ground (minus.) It's the same circuit and easier for me to understand.

Why didn't someone tell me about vinegar BEFORE I took a wire brush attachment on a Dremel type tool to clean them and wrecked them? BTW I think they're 25 watts. I think I'm going to replace mine with L pads. There are very few speakers that use potentiometers as volume controls. The reason is simple, as the control position is changed, so is the crossover frequency. BTW, the AR2axs still work great.

One problem with AR2a I noticed was the warpage of the cones on all of the 5" Jensen the midrange drivers. When I visited Bill at Millersound he was manufacturing new cones for these drivers for someone who wanted an authentic restoration. I still haven't decided what to do with them yet. Hey, It's only been about 7 or 8 years. Give it time, give it time. :)

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I don't see any other caps

Odd. On mine the small can off to the side is marked 2x2uF so that's the 4. I can't read the printing on the larger bundle but undoubtedly it comprises the 6uF. Somewhere in your boxes there has to be one 6uF equivalent and one 4uF equivalent. The only marking visible is 2uF.

Those grilles are a bit of a PITA IIRC. I broke one removing it--it must be bowed to slip into the slots on the short sides of the frames but mine was also glued to the plastic frame of the angled tweeter (mid) housing. Think there were also some cardboard shims in there. I was able to glue the broken fiberboard back together using epoxy and a reinforcing layer of brown Kraft paper. Fiberglass may have been better but the saturated paper seems to have worked fine. Then I replaced the grille without the glue.

-Kent

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dxho, I like the way you drew the schematic. It's closer to how I've redrawn it. The way many people draw schematics and wiring diagrams drives me nuts. I sometimes have to redraw them just to understand them. I also don't understand why the caps for the mid and tweeter aren't in series on the + side of the input and the speakers connected from the sliding contactor terminal 3 to ground (minus.) It's the same circuit and easier for me to understand.

Why didn't someone tell me about vinegar BEFORE I took a wire brush attachment on a Dremel type tool to clean them and wrecked them? BTW I think they're 25 watts. I think I'm going to replace mine with L pads. There are very few speakers that use potentiometers as volume controls. The reason is simple, as the control position is changed, so is the crossover frequency. BTW, the AR2axs still work great.

One problem with AR2a I noticed was the warpage of the cones on all of the 5" Jensen the midrange drivers. When I visited Bill at Millersound he was manufacturing new cones for these drivers for someone who wanted an authentic restoration. I still haven't decided what to do with them yet. Hey, It's only been about 7 or 8 years. Give it time, give it time. :)

Just to clarify a few points:

-For those who may not know...AR schematics are often drawn showing the caps in series with the #1 (negative) side because that is how those particular models were wired. In fact, most AR models well into the 70's were wired in this way.

-No amount of vinegar will take care of most of the corroded AR pots out there. If caked, green corrosion has developed, there will always be pits under it. Sandpaper or a Dremel tool may be of help in these cases. If the corrosion is too bad I toss it.

-The dual AR-2/2a cones are extememly thin and fragile. The distortion of the cones is due to fiberglass packed under it. They were likely that way from the factory.

-I agree with Kent. The oil filled type caps seen in the above photos are seldom out of spec unless signs of leakage can be observed. AR very often bundled various values, or "dual" caps with multiple taps, to obtain the desired values for the crossovers...probably using whatever was available to the company at the time. The larger bundle above is the 6uf cap.

Roy

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Odd. On mine the small can off to the side is marked 2x2uF so that's the 4. I can't read the printing on the larger bundle but undoubtedly it comprises the 6uF. Somewhere in your boxes there has to be one 6uF equivalent and one 4uF equivalent. The only marking visible is 2uF.

-Kent

I got a look at the wired end of the caps. The large 2uf on the top is wired to one of the smaller sqaure ones. conclusion: large 2uf and smaller 4uf in series makes 6 uf. Single smaller 4 uf alone.

The interior of the pots is actually very clean. bright metal and no corrosion, at least on the first one. I pulled the first one apart to access the wipers.

Clean the pots, and have a listen.

Glen

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The caps in the second box are different.

Bummer. The wax block SHOULD be replaced. So the question is; do you re-cap both speakers so they match or leave the oil caps? I'd like to know Roy's opinion. Of course if you do replace the oil caps you could sell them on ebay, probably for a respectable sum.

-Kent

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Bummer. The wax block SHOULD be replaced. So the question is; do you re-cap both speakers so they match or leave the oil caps? I'd like to know Roy's opinion. Of course if you do replace the oil caps you could sell them on ebay, probably for a respectable sum.

-Kent

I would replace the caps in both cabinets.

Roy

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The mids have no contact with the fiberglass in these boxes. The housing is solid behind them.

first pot cleaned. Highs have been restored.

The fiberglass I am referring to is part of the construction of the drivers. It has nothing to do with the fiberglass in the cabinet. It is the primary reason for the irregularities seen in the paper cones.

Roy

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Just to clarify a few points:

-No amount of vinegar will take care of most of the corroded AR pots out there. If caked, green corrosion has developed, there will always be pits under it. Sandpaper or a Dremel tool may be of help in these cases. If the corrosion is too bad I toss it.

Roy

Perhaps these were in the minority. I did use a small wire hand brush to help finish the cleaning, after an overnight soak in the vinegar. These particular pots hadn't lost much material, except for the rivet holding the round disc on this one.

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Perhaps these were in the minority. I did use a small wire hand brush to help finish the cleaning, after an overnight soak in the vinegar. These particular pots hadn't lost much material, except for the rivet holding the round disc on this one.

Those are the early version, which have much better construction...and from your photos, were well worth restoring. The type of corrosion I was referring to will often chew through the wiper and disc.

Roy

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I would replace the caps in both cabinets.

Roy

I have started that re-cap on both. They need to match and the non oil cap speakers were pretty lame overall anyway.

My apologies and thanks to Audiophile03 for using this thread to help restore my AR-2A.

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