troppo Posted March 7, 2012 Report Share Posted March 7, 2012 Troppo here;I started working on my 3a project and I am already in trouble. My speakers have the Sprague electrolytics instead of the large Industrial Condenser. What's the deal with the Spragues ?? Should I use the Spragues combined with a new tweeter cap ? Also, I'm thinking of just cleaning up the old pots and re-installing them instead of using the new rheostats.Every example of a crossover upgrade that I have seen seems to be different, with three or four caps. (I'm especially refering to the classic, clean crossover mod job that has just recently been submitted to these pages). I'm a pretty good connect-the-dots guy but weak when it comes to electronoc innovation. I could use some advice.Troppo Link to comment Share on other sites More sharing options...
Carlspeak Posted March 7, 2012 Report Share Posted March 7, 2012 I've recently tested some Sprague Compulytic caps and found they tested very well; a testimate to their longevity. Visit this linkhttp://www.classicsp...indpost&p=90734Also download and read the attachments at post #4 at that link for an explanation of those test charts.My recommendation is to not change the 50 and 150 Sprague caps. If you want, just do the tweeter cap with a film cap. Link to comment Share on other sites More sharing options...
RoyC Posted March 7, 2012 Report Share Posted March 7, 2012 I agree with Carl. There is much evidence to support his results. In fact, if you are fortunate enough to have all Sprague capacitors, including the 6uf tweeter caps, you may just want to refurbish the pots, re-foam the woofers, and take them for a test drive.The Sprague capacitors were used in later AR-3a's, beginning sometime in 1972 or early 1973. What are the serial numbers on the cabinets?Roy Link to comment Share on other sites More sharing options...
danajohnhill Posted March 7, 2012 Report Share Posted March 7, 2012 I am a big proponent of reusing the original pots. Clean them with the soft wire brush wheel on a Dremel tool. It gets the funk off no problem. Link to comment Share on other sites More sharing options...
ar_pro Posted March 7, 2012 Report Share Posted March 7, 2012 The Dremel tool certainly can do an excellent job - if there's enough metal left.Not infrequently, there's more corrosion than conductor, but if they're restorable, I'd always opt for the original pots. Link to comment Share on other sites More sharing options...
troppo Posted March 7, 2012 Author Report Share Posted March 7, 2012 I agree with Carl. There is much evidence to support his results. In fact, if you are fortunate enough to have all Sprague capacitors, including the 6uf tweeter caps, you may just want to refurbish the pots, re-foam the woofers, and take them for a test drive.The Sprague capacitors were used in later AR-3a's, beginning sometime in 1972 or early 1973. What are the serial numbers on the cabinets?Roy My speaker are #59526, and #59534 Link to comment Share on other sites More sharing options...
RoyC Posted March 7, 2012 Report Share Posted March 7, 2012 The Dremel tool certainly can do an excellent job - if there's enough metal left.Not infrequently, there's more corrosion than conductor, but if they're restorable, I'd always opt for the original pots.I agree...and care must be taken not to damage the coil of resistor wire, which is seldom affected by corrosion. Some of the caked green corrosion will leave pits, and/or produce tiny holes in the wipers.Roy Link to comment Share on other sites More sharing options...
RoyC Posted March 7, 2012 Report Share Posted March 7, 2012 My speaker are #59526, and #59534The manufacuture date of your speakers is sometime in mid-1971, which means the Sprague caps were being used earlier than we previously thought in the 3a. Come to think of it, I have seen some '71 era AR-4x's with Spragues.Thanks!Roy Link to comment Share on other sites More sharing options...
troppo Posted March 9, 2012 Author Report Share Posted March 9, 2012 Hi;Troppo again,I pulled the Sprague Catalytics out. One is labeled 50 MFD-50 VNP. +10%, -10% VNP.The other Sprague says 150 MFD, etc. What does this mean??T Link to comment Share on other sites More sharing options...
ironlake Posted March 9, 2012 Report Share Posted March 9, 2012 50 = 50 microfarad which is the value of the cap, + 10% - 10% means the amount of varance in value the caps can have Link to comment Share on other sites More sharing options...
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