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That 20 ft coax could be picking up some signal. Here's way more information than you probably need, but the coiled-coax balun might help. http://ham-radio.com/k6sti/balun.htm

Looks like it ran from at least '74 through '78, based on buyers guides. The CT-38 was apparently a one-year model ('78). CT-38 Two-Way Speaker System Two-way speaker system with two 8-1/4" woofers and two 2-1/2" tweeters; min. input 10 W rms; max. input 75 W/ch rms; 4-ohm imp.; hand oiled oak veneer accent panels, wrap-around cloth panels, and removable smoked glass top; 41" H x 11" W x 11" D $250.00

Good to know these pots aren't indestructible. Yours is the first field report of which I'm aware.

There are 2 x 2uf caps lashed together. Three are connected to make the 6uf, and one is run separately. I replaced the oil caps in my pair; the sound did not noticeably improve. But that would only affect the tweeters, and these don't go that high in the best of circumstances. The pots on these are unique to this model, and apparently do not corrode. At any rate, I'd test the caps and pots before arbitrarily replacing them. This might be one of the few vintage systems that legitimately doesn't need upgrading. Kent is right about the possible use of surround sealer. These are capable of prodigious bass.

I'll add that it's probably worth the effort to set the ARs in the bookshelf and gauge performance...

The bigger furniture stores and new car dealer parts departments typically have massive amounts of cardboard to handle and often are fine with scavenging. They usually have the biggest boxes.

The high-end KLH tweeters from a certain time period look the same, but there are two variations, apparently with different voicing:

Usual advice is to keep the originals. I tested that advice and found new caps did not change the sound. You are certainly welcome. This exact model was my gateway drug to this website and all things AR, so I'm happy to enable others ?

Those are indeed original AR-2 pots.

Does it look like this?

I think it's quite an accomplishment! Thank you for detailing the process. You might be the first person, to my knowledge, who did so. I think a couple of reasons (and probably others, no doubt) for no response: there is one person, maybe two, who are now offering repair services here, and there's finally a reasonably close-in-sound aftermarket replacement available. Nevertheless, I may finally drag out the dead tweeters I've been hanging onto for several years and see if they can be revived.

They were made from ~'71-'76. Yours would appear to be early in that range. What requires knowing their age?

Production started apprx 3/58, so probably not too long after that.

Here's a listing of the early KLH products I pulled together. The one at the top of this thread has a lot of mistakes. http://www.aphenos.net/electronics/speakers/klh/all_klh.htm

Looks like they were sold from 1989-91 Features treated paper woofer and liquid-cooled tweeter; direct-coupled woofer; dual-density baffle; frameless grille; acoustic-suspension enclosure. Walnut or black-ash woodgrain vinyl finish. Power handling 10-60 W; frequency response 65-25,000 Hz, -3 dB; sensitivity 90 dB; impedance 8 ohms. 14 x 7-1/2 x 7-3/8 in; 9 lb. 4 oz $289/pr

Lots of folks out there happy to sell you new drivers, but you probably don't need them. The foam surrounds can be replaced, at considerably less cost. And if some are bad, all of them need to be done. I wouldn't run the speakers at all. Too easy to damage drivers that need surrounds.

Earliest instance of which I'm aware is the KLH Model Four tweet, ~1958.

New (.pdf) version, many corrections. AR_Drawings_.pdf

appears to be some activity at audiokarma.org

Sorry, thought you were confined to AC current. Looks like you already have a solution.

Is it worth considering LEDs with some sort of diode arrangement? Lots more light for the watts...

Yes, very nice signs.

I've seen Sixes in the 70xxx serial range with glued in tweeters, so this example is a bit confusing. But I'll add it to the list :-)

these work nicely: https://www.ebay.com/itm/8pcs-Antique-Brass-Plated-Brass-Base-Center-Hole-Round-Disc-14mm-1871C-U-299/401173375672?hash=item5d67cbeab8:g:WPQAAOSwPYZU9htH

Depends on your toolbox and attention span :-) I'd probably escalate tactics until I got it turned or broke it/ proved I couldn't turn it. Nothing to lose, really.