Pots for older AR's

[Guest tomgiffen]

I recently acquired a pair of AR2Ax's, very good overall, good veneer, original grill cloth, good mids/tweets, needing a refoam... and with the dreaded dead pot disease. After looking thru the posts on the subject, I decided to check around for replacements of the original values. The closest pots seemed to be Ohmite RHS15's, 15 ohm, 25 watt. Mouser had them, but a little steep at $25 each, so I checked on the web using Google. Ended up buying 4 for $8 apiece from an electronics surplus vendor in Florida. Will advise further after receipt. These may be slightly off for 2ax's, but would be on the money for 3a's. If interested, here's the URL: http://www.skycraftsurplus.com/index.asp?P...TS&Category=179

[tysontom]

>I recently acquired a pair of AR2Ax's, very good overall,

>good veneer, original grill cloth, good mids/tweets, needing a

>refoam... and with the dreaded dead pot disease. After looking

>thru the posts on the subject, I decided to check around for

>replacements of the original values. The closest pots seemed

>to be Ohmite RHS15's, 15 ohm, 25 watt. Mouser had them, but a

>little steep at $25 each, so I checked on the web using

>Google. Ended up buying 4 for $8 apiece from an electronics

>surplus vendor in Florida. Will advise further after receipt.

>These may be slightly off for 2ax's, but would be on the money

>for 3a's. If interested, here's the URL:

>http://www.skycraftsurplus.com/index.asp?P...TS&Category=179

As you may or may not know, you *can* rebuild the existing level controls with a little effort if they aren't completely oxidized. They can be disassembled, cleaned and reinstalled for another 40 years of service. Try that method first before retrofitting another type control, which may or may not work as well in the end.

--Tom Tyson

Fig. 1: Pollock level control

Fig. 2: Disassembled unit

Fig. 3: Using a Dremel tool to wire-brush the contact surfaces

Fig. 4: Proper disassembly and reassembly of control is important.

http://www.classicspeakerpages.net/dc/user_files/384.jpg

http://www.classicspeakerpages.net/dc/user_files/385.jpg

http://www.classicspeakerpages.net/dc/user_files/386.jpg

http://www.classicspeakerpages.net/dc/user_files/387.jpg

[Guest tomgiffen]

Thanks for the input. Since I wanted to hear the speakers before the new pots would arrive, I took the Pollock pots apart. One of the four was in reasonable shape. I was able to clean it to a satisfactory degree using a fiberglass contact burnishing tool. The other three were considerably more rough. There was a substantial buildup of what appears to be copper sulfate- bluish, powdery, crud. I used the Dremel with a wire brush on these. After cleaning, one wiper actually had a perforation where it would meet the windings. I repaired the hole with solder, and got all the pots to the point where I got a fairly smooth sweep with my DMM, with relatively few "dropouts". The resistance value measured approximately 15.4 ohms on all pots.

Much to my chagrin, I found that I have one tweeter with an open voice coil. Does anyone on the list have a spare tweeter, with the 3/4" black dome and external wiring, that they may wish to sell? I also need a grill badge of the inlaid brass style, reading "AR2ax". I would welcome any help or suggestions. I have and will continue to haunt Ebay... where I bought the project in the first place.

[dynaco_dan]

Hello there

Just a compliment on the excellent quality photos, Tom.

[RoyC]

I've been trying out some replacement (15 ohm) pots in AR-5's and like them very much. Sometimes the old ones are too far gone to bother with.

At least yours all measured in the same 15+ range. I've had some that measured close to 17 ohms. I used to think there were different impedances for the various models, but there doesn't seem to be any rhyme or reason to the variations. The typical AR pot/rheostat seems to measure between 15 and 16 ohms regardless of the rated impedance of the speaker system.

When you install your new pots protect the back of them with something to prevent the cabinet stuffing from getting into them. One advantage of the the originals is the protective rear cover.

When you search for tweeters be aware that the AR-2ax uses the same 8 ohm tweeter as the AR-5, not the 4 ohm AR-3a tweeter. They are a bit tougher to find.

Roy

[tysontom]

>Hello there

>

>Just a compliment on the excellent quality photos, Tom.

Thanks, Vern. I wasn't sure that everyone could view the images due to the quirky way in which I had to post them, but I'm glad that they came up okay.

--Tom Tyson