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Curt55

My Dads AR1s

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Hi all, I am a new member but have been lurking recently.  I am about to get behind the AR1 woofer and replace the cap with a  Solon PB 24UF and the rheostat. The rheostats I plan to use are military aircraft surplus 17 ohm  50 watt. They came in a sealed aluminum clad bag with desiccant  and a colored dot indicator that reacted to the humidity slowly after I opened the bag. Very cool I thought. They were packaged in 1960.  Here is a photo of one woofer and 755.     I have a questions about the woofer.   Do you think the surround needs more goo  ( is that the correct term). When I depress the cone rebounds slowly and takes about 2 seconds.    I have been successful in the past with newer drivers using a slight vacuum to repair  dust caps, and dome tweeters.  Should I try that or leave well enough alone.   It looks like it is going to be a bear to release the woofer from the sealant, slow and careful I will go.  Electrical duct seal is what I plan to use for re bedding. 

Here are some photos

 

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The woofer return sounds fine.

If your original caps are oil filled metal cans and they don't show signs of leakage or other damage there should be no need to replace them. 

Replacing the original 15 ohm pot with a 17 ohm rheostat is a 13% increase in resistance that will change the mids and highs from the 755. Also, the rheostat appears in the photo to be a two terminal unit rather than three. If so, it's definitely not a suitable replacement part.

Is the original pot not restorable?

More pics would be useful, especially of the insides as you open them up.

 

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What Gene said.

Also--this is a rare and collectible speaker, not to mention the emotional attachment (I assume). If you can leave it 100% original that would be a good idea.

-Kent

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Thanks guys, I see the light. 

Do you  think I need to get to the original pots. There are some dead spots  but I can live with it . 

The cabinets are unfinished and not in great shape.  My thinking was to fabricate new cherry trim and apply cherry veneer. I am a retired woodworker so my fabricated trim would be an exact replica. 

Those aircraft rheostats have the 3rd tap inside the covers and my thinking was I could silver solder over some coils at one end to get to 15 ohms.   I will save that experiment for a pair of 3a. I think they require 16 ohm.

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The rheostats I plan to use are military aircraft surplus 17 ohm  50 watt

 

Dude just hold on to it. as @JKent said, the sentimental value is priceless and even without it. Put them aside for now. BTW, thanks for the pics. However I do like the idea that you're trying to restore it. My gut is saying just leave it as it is :)

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If all you have are a few dead spots, odds are you can just clean the pots and they'll be fine.

I suggest you post pictures of the cabinets from all angles and see if the woodworkers here have any suggestions. Unless they look like termites have been chewing away at them, they can probably be cleaned up and refreshed without having to do anything that will negatively impact their original look.

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As far as the dust cap I have taken a small sliver (maybe 1/4 in wide) of some sticky duck tape and folded a small tab on the end and applied it carefully to the dent with a pen tip and pulled quite a bit of the dent out. 

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I decided to do nothing. I can live with a few dead spots  on the rheostats. Here are some photos of the cabinets , and what I did in the meantime.  If you think leaving the cabinets original is best , I will take your advice.  I would like to veneer them though if it would not hurt the value.

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What's going on with the front of the frame? Is that some kind of tape peeling off?

I would sand them and see if it's possible to clean the wood. If you want to veneer, you'll need to that anyway.

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My Dad had them built into the wall and he had a magnetic catch , you can see the two screw holes, that secured a louvered shutter that was hinged. I can only guess that my Mom requested the shutter, but who knows. They were in the living room wall.  I can easily fabricate new trim out of cherry and the veneer the raw wood cabinets.

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the holes in the frame don't look to be very big and can likely be made invisible with good filling technique. I could be wrong but I believe they are Birch.

 

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Unfinished cabinets were white pine with white birch face frames. It's ironic that decades later these "utility" cabinets are actually more valuable to collectors than the cabinets with furniture grade veneers, but if you're concerned about not hurting the value, your first attempt should be to restore the look of the unfinished wood when it first came out of the box.

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All this talk about cabinets......but what's going on inside these cabinets? Where did all of those extra and newer components come from? I'm just not sure what we're looking at here..... :blink: Perhaps this schematic is incorrect? ...I just dunno....

AR-1 schematic pot.jpg

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There's this schematic, but I still see only two choke coils:

Just wondering about two things - was there a problem with the original capacitor, and wasn't fiberglass packed around the 755A in its sub-enclosure?

ar1.jpg

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Sorry I should have been more specific.  The last two photos are of where I focused my attention when I decided not to do anything to the AR1.  They are my work in progress rebuilding the crossovers in a pair of AR3a

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1 hour ago, Curt55 said:

Sorry I should have been more specific. 

Yes, that does explain a few things....... :lol:

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