Mexicomike Posted June 4, 2008 Report Share Posted June 4, 2008 HI Guys,I arrived yesterday back home (Mexico) after 6 weeks in the US, bringing with me all the caps to recap my LSTs.There is an original Sprague Compulytic 2500 MFD cap in one of the Xovers and a group of 4 5000 MFDs in the other LST. I am replacing both with new 2500MFD caps. I have discoverd that the Sprague is actually split open so I suspect its capacitance was off a bit! Anyway, here's the question, the original Sprague does not have either of it's terminals marked with a + or - or any other type of marking (like the arvious shapes that are also used on some caps). So I don't know which terminal is which, which means I don't know how to connect the new 2500 Ohm cap. I'm confused. Does it not matter which way the cap is connected or am I just missing something obvious on the old cap? The new ones have a + next to one terminal. Link to comment Share on other sites More sharing options...
KlausDK Posted June 4, 2008 Report Share Posted June 4, 2008 Anyway, here's the question, the original Sprague does not have either of it's terminals marked with a + or - or any other type of marking. So I don't know which terminal is which, which means I don't know how to connect the new 2500 uF cap. I'm confused. Does it not matter which way the cap is connected or am I just missing something obvious on the old cap? The new ones have a + next to one terminal.The Capacitors used in speaker cross-over's are bi-polar (or non-polar or reversable polarity), as is the case with the 2500 uF Sprague, hence the missing markings. If you have bought a capacitor marked with "plus" and "minus", you cannot use it as a 1 to 1 replacement of a bi-polar cap. You have to find a bi-polar cap to replace it. I would also recommend a by-pass with at least one smaller cap, e.g. a 1-2 uF film cap (polypropylene) to compensate for the high ESR of the 2500 uF capacitor at high frequencies.Take a look at this post for availability of this kind of capacitor: http://www.classicspeakerpages.net/IP.Boar...?showtopic=1932BRgds Klaus Link to comment Share on other sites More sharing options...
Carlspeak Posted June 4, 2008 Report Share Posted June 4, 2008 I recently recapped a pair of orig. LST's and mistakenly bought a pair of Sprague 2500 uF electrolytic caps. However, when I got them I saw a + sign printed on one end. A phone call to my supplier confirmed they were polar caps. NG for xovers.I did some more searching and ended up purchasing two 1000 uF and one 500 uF Bennic NPE's from Madisound for each speaker. So, there's a state side source of a cap bundle for your LST's. Link to comment Share on other sites More sharing options...
Mexicomike Posted June 4, 2008 Author Report Share Posted June 4, 2008 Oh well...I messed that up and looks like I also bought the wrong caps for the midrange - I swear I needed 50mfd and that's what I bought but the originals use 40mfd (a 30, a 6 and a 4!) So the LSTs are on hold again until I go back to the States in September/return here in October and start over. Bummer! Link to comment Share on other sites More sharing options...
Mexicomike Posted June 4, 2008 Author Report Share Posted June 4, 2008 Now I'm even more confused. The other LST has the gang of 4 5000mfd capacitors (wired I guess in series/parallel). Each of those caps have 4 terminals around the side, all attached to the can, and one terminal in the center with a half-circle symbol next to the terminal. Doesn't this indicate that is a + terminal and that therefore these are polarized caps? Link to comment Share on other sites More sharing options...
KlausDK Posted June 4, 2008 Report Share Posted June 4, 2008 Now I'm even more confused. The other LST has the gang of 4 5000mfd capacitors (wired I guess in series/parallel). Each of those caps have 4 terminals around the side, all attached to the can, and one terminal in the center with a half-circle symbol next to the terminal. Doesn't this indicate that is a + terminal and that therefore these are polarized caps?Hi MikeYes, thats why I wrote that you cannot make a 1 to 1 substitution, but you can make an arrangement like the one on your oldest LST, but that would require more than 1 polarized cap per speaker and you should mount them plus to plus or minus to minus, I don't remember, you can see how they are mounted on your LST's.BRgds Klaus Link to comment Share on other sites More sharing options...
Mexicomike Posted June 4, 2008 Author Report Share Posted June 4, 2008 Right - I understand now, I think... I could take the two 2500s and connect them to each other via the + terminal, then to the circuit using the other terminals and they would function as a non-polar. But, of course, I'd still need two more for the 2nd LST anyway, so coupled with the fact that I also have the wrong mid caps (50 mfd instead of 40) I can't do anything with it now anyway. I wonder why AR went with 40MFD on the LST mids instead of 50Mfd as on the 3a. The drivers are the same... Link to comment Share on other sites More sharing options...
KlausDK Posted June 4, 2008 Report Share Posted June 4, 2008 I wonder why AR went with 40MFD on the LST mids instead of 50Mfd as on the 3a. The drivers are the same...The X-overs differs by the Rheostats, that might be the reason....BRgds Klaus Link to comment Share on other sites More sharing options...
KlausDK Posted June 6, 2008 Report Share Posted June 6, 2008 And one more thing, you buy the 2 amp (FNM 2) Bussmann Fusetron fuses for only 1½$ each here (for LST and AR-11):http://www.electronicsurplus.com/commerce/...d=1212787291201 They still have 300+ in stock.BRgds KLaus Link to comment Share on other sites More sharing options...
Mexicomike Posted June 7, 2008 Author Report Share Posted June 7, 2008 Excellent! Thanks Klaus, I was wondering where to get those fuses!I'm trying to figure out how to get the proper caps sent here to me in Mexico without paying a foolish amount of duty. The first (and only) time I tried this was when I ordered a USB SD card reader from the States. The card reader was $39; the duty was $31 !!! It's not that I couldn't afford the caps + duty but I find it very annoying; I don't think the the US gets anything out of our "partnership" with Mexico anyway and...Oops, sorry. I almost stepped to the top of that particular soap box. Link to comment Share on other sites More sharing options...
Diamonds&Rust Posted June 8, 2008 Report Share Posted June 8, 2008 I'm trying to figure out how to get the proper caps sent here to me in MexicoNot so fast, Mike.I don't remember if it was the Callins or the Spragues, but one set of those old 2500uF caps CLEARLY had a "+" on the top by one terminal...BUT !!!It was a non-polar capacitor just the same. Said so right on it.My guess is that they used the same end-cap for more than one capacitor and since it didn't matter which terminal was "+" on a non-polar, they didn't worry about its being there when it didn't need to be.Got that?The fact that there is a "+" by one capacitor terminal doesn't prove much of anything. It's evidence, sure, but it proves nothing.Anybody know an easy way for Mike to tell if he has a non-polar cap?Bret Link to comment Share on other sites More sharing options...
johnieo Posted June 8, 2008 Report Share Posted June 8, 2008 Not so fast, Mike.The fact that there is a "+" by one capacitor terminal doesn't prove much of anything. It's evidence, sure, but it proves nothing.Anybody know an easy way for Mike to tell if he has a non-polar cap?BretYes, one can tell by looking for the letters "NP" on the can. Please see the attached photo of Callins and Sprague that for sure are NP. Yes, they too have a + sign, and I did not pick up on that! Thanks, Bret!Cheers Link to comment Share on other sites More sharing options...
Mexicomike Posted June 8, 2008 Author Report Share Posted June 8, 2008 Thanks all - Here's a pic of the new cap and the original cap. If I've learned my lessons correctly over the past few days (Thanks, John O!) the new cap is definitely polarized and the old is not. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.