Rubber Duck Posted April 27, 2011 Report Share Posted April 27, 2011 Hi I will be replacing the caps on my AR11s. I have attached a photo of the crossover and would appreciate some varification that I am on the right track. Is the large silver canister the 122 uF cap with the smaller black tubes the 40 and 10uF caps?Thanks Link to comment Share on other sites More sharing options...
deek Posted April 27, 2011 Report Share Posted April 27, 2011 All the capacitors are clearly marked. I can see the rating on the 10 and 40 uf caps in your photo. If you rotate the large canister around you'll find markings on it as well.Why are you replacing them? Do you see signs of leakage? Do you suspect them to be faulty? I see no signs of swelling or corrosion...-Deek Link to comment Share on other sites More sharing options...
Rubber Duck Posted April 27, 2011 Author Report Share Posted April 27, 2011 All the capacitors are clearly marked. I can see the rating on the 10 and 40 uf caps in your photo. If you rotate the large canister around you'll find markings on it as well.Why are you replacing them? Do you see signs of leakage? Do you suspect them to be faulty? I see no signs of swelling or corrosion...-DeekHiI had assumed based on what I have read that they would need to be replaced just because of their age. There is no sign of problems with them that I can see. Should I leave them? Link to comment Share on other sites More sharing options...
deek Posted April 27, 2011 Report Share Posted April 27, 2011 Having just measured the caps in my AR9 (circa 1980) I'm not convinced that there are many capacitors of that age that truly need replacing.All 5 of the caps in the tweet/umid/lmid circuit on both of my 9's were within 5% of their advertised rating. To be honest I felt a little dumb for going through the exercise; as I was de-soldering them I was thinking "these caps look to be in perfect condition; I wonder if I should even bother?" I shouldn't have, as it turns out!Don't get me wrong; I'm not saying capacitors last forever or that AR caps never need replacing... I just haven't seen any evidence in speakers of that particular vintage that are in need of replacement.How do the speakers sound? (If you've been able to listen to them, that is) If you don't notice any unnatural artifacts in critical listening exercises, I think you're fine.I would like some others to weigh in, but my opinion is that capacitors of that type and of that age are not prone to failure except in extreme conditions.-Deek[EDIT] typed "tweeters" instead of "caps" [/EDIT] Link to comment Share on other sites More sharing options...
deek Posted April 27, 2011 Report Share Posted April 27, 2011 It's worth noting that I didn't measure the large caps in the 9's woofer circuit. Those most closely match the type and size of the large capacitor in your 11's. (No real point, just full disclosure)If you have a college in your area that has an electronics lab, they will be able to measure the capacitance of those parts easily. (that's what I did)-Deek Link to comment Share on other sites More sharing options...
JKent Posted April 27, 2011 Report Share Posted April 27, 2011 HiI had assumed based on what I have read that they would need to be replaced just because of their age. There is no sign of problems with them that I can see. Should I leave them?HiIt's my understanding that those black caps with red ends, sometimes called "Callins type" are PVC with poorly sealed ends, and very prone to leakage. The caps like that in my KLH Model Seventeens had actually exploded! I say replace them. OTOH, that big can may be OK. You could measure it.Kent Link to comment Share on other sites More sharing options...
soundminded Posted April 27, 2011 Report Share Posted April 27, 2011 Hi I will be replacing the caps on my AR11s. I have attached a photo of the crossover and would appreciate some varification that I am on the right track. Is the large silver canister the 122 uF cap with the smaller black tubes the 40 and 10uF caps?ThanksReplacing the caps is the correct thing to do. Don't be fooled by appearances, these old caps change value over time without any external sign. They only leak when failure is far along and catastrophic. As the paper dielectric inside erodes, the capacitance increases lowering the high pass frequency to drivers they are in series with, the tweeter and midrange. This puts them at risk and since they are for all practical purposes irreplacable if you have original ones in good working order, this is a smart move. I recapped my AR9s and some of the old caps were well out of spec. The only ones I left alone were the two biggest cans. Whatever theory you believe in regarding capacitor quality vis a vis sound, recapping them makes sense. Personally I used Parts Express's cheapest NPC. The treble definitely improved. Link to comment Share on other sites More sharing options...
michiganpat Posted April 27, 2011 Report Share Posted April 27, 2011 Replacing the caps is the correct thing to do. Don't be fooled by appearances, these old caps change value over time without any external sign. They only leak when failure is far along and catastrophic. As the paper dielectric inside erodes, the capacitance increases lowering the high pass frequency to drivers they are in series with, the tweeter and midrange. This puts them at risk and since they are for all practical purposes irreplacable if you have original ones in good working order, this is a smart move. I recapped my AR9s and some of the old caps were well out of spec. The only ones I left alone were the two biggest cans. Whatever theory you believe in regarding capacitor quality vis a vis sound, recapping them makes sense. Personally I used Parts Express's cheapest NPC. The treble definitely improved.the big cannister one is probably OK to leave, the 2 smaller I'd replace for the reasons soundminded listed. Link to comment Share on other sites More sharing options...
Carlspeak Posted April 27, 2011 Report Share Posted April 27, 2011 Most or all of those black caps with the red ends are going on my 'bad boy' list. IMO, they were ALL made by the same company and printed whatever was needed on them for different customers. I'm currently working on a Fisher XP-9C xover with a bunch of the same type 'bad boys' Some are marked 'temple', others 'whale'. However, they all look the same. Just tested a 12 uF 'whale' from that xover midrange section and its ESR was about 2.5 ohms and the capacitance ranged from 7.8 uF to 11.9 over the 10 hz - 20 kHz range. Link to comment Share on other sites More sharing options...
RoyC Posted April 27, 2011 Report Share Posted April 27, 2011 Most or all of those black caps with the red ends are going on my 'bad boy' list. IMO, they were ALL made by the same company and printed whatever was needed on them for different customers. I'm currently working on a Fisher XP-9C xover with a bunch of the same type 'bad boys' Some are marked 'temple', others 'whale'. However, they all look the same. Just tested a 12 uF 'whale' from that xover midrange section and its ESR was about 2.5 ohms and the capacitance ranged from 7.8 uF to 11.9 over the 10 hz - 20 kHz range.My experience agrees with Carl's.If the large silver cap is labeled as "Sprague Compulytic", it is probably worth keeping. It is likely better than any modern inexpensive electrolytic capacitor.Roy Link to comment Share on other sites More sharing options...
JKent Posted April 27, 2011 Report Share Posted April 27, 2011 HiIt's my understanding that those black caps with red ends, sometimes called "Callins type" are PVC with poorly sealed ends, and very prone to leakage. The caps like that in my KLH Model Seventeens had actually exploded! I say replace them. OTOH, that big can may be OK. You could measure it.KentFWIW, Carli caps from Madisound are good and economical. You could use two 20uF @ $5 ea for the 40. Carli 10uF is $2.30 ea. OR Madisound has some surplus polypro 10uF film caps for 0.60 each. Heck, there's enough room. Why not buy 10 of the 10uF for a grand total of $6 and bundle 4 for each of the 40uF values? A bargain!Kent Link to comment Share on other sites More sharing options...
Rubber Duck Posted April 27, 2011 Author Report Share Posted April 27, 2011 Thanks to all for your advice. The caps will go! Link to comment Share on other sites More sharing options...
deek Posted April 29, 2011 Report Share Posted April 29, 2011 So I have some uber-robust caps in my 9's or the university snowed me over.I agree the price (and the work for that matter) is fairly inconsequential so there's no harm of course.I wonder why my experience is so different from the others?-Deek Link to comment Share on other sites More sharing options...
michiganpat Posted April 29, 2011 Report Share Posted April 29, 2011 So I have some uber-robust caps in my 9's or the university snowed me over.I agree the price (and the work for that matter) is fairly inconsequential so there's no harm of course.I wonder why my experience is so different from the others?-Deekdid you also measure resistance?maybe you got lucky... Link to comment Share on other sites More sharing options...
deek Posted April 30, 2011 Report Share Posted April 30, 2011 Nope. They sent them back to me with post-it notes stuck on them with the capacitance value on them.Didn't even think to measure resistance.* now where's that soldering iron... *-Deek Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.