gagelle Posted July 21, 2011 Share Posted July 21, 2011 I did some extensive reading in this subject last night and found that there are still disagreements between experienced technicians on this subject. After my brief study, I decided that a complete overhaul, including all caps, is necessary on a unit over 30 years old.The argument that made the most sense to me is that one can't just test individual parts and conclude that everything is working well even if those parts are operating within specifications.One has to look at the unit as a whole. Every part affects every other, and eventually affects the whole. As an example: The electrolytics store energy. As they start to fail, it makes the unit pull more current, which produces more heat that can degrade other parts. Everything is linked. The tech who partially restored my Sansui AU-717, when I asked him if he replaced the Electrolytics, said that it's not necessary, they tested within specs. (Same argument.) He said he has seen them last for 50 years or more. I don't buy it. They're not made to last that long. They may work, but they degrade over time. I'm also convinced that restoring vintage equipment is an art. That's why, IMHO, there are 2 month waiting periods for certain technicians. More than just installing parts, vision and intuition are needed for a high quality restoration. "O Nature, and O soul of man! how far beyond all utterance are your linked analogies!" --Moby-Dick, by Herman Melville Quote Link to comment Share on other sites More sharing options...
JL Sargent Posted July 21, 2011 Share Posted July 21, 2011 You've heard that old saying "if you don't use it, you will lose it". Well that can really be true when it comes to caps. Vintage equipment that is used all the time may very well have caps that are working properly. You take that same equipment and store it for 20yrs, then plug it up and you'll likely have caps that have "dried up". Sometimes you can revitalize caps in old equipment especially crossovers. I had a pair of muffled sounding crossovers once. They were just terrible sounding. I left them playing music unattended for a week or so and they started sounded much better. It was like they had woken up. I went ahead and rebuilt them though and that was yet again another improvement. The point is: There are no hard rules to cap life. Some will last longer than others. You get to decide when is long enough on your stuff. Quote Link to comment Share on other sites More sharing options...
tube fanatic Posted July 21, 2011 Share Posted July 21, 2011 You've heard that old saying "if you don't use it, you will lose it". Well that can really be true when it comes to caps. Vintage equipment that is used all the time may very well have caps that are working properly. You take that same equipment and store it for 20yrs, then plug it up and you'll likely have caps that have "dried up". Exactly! Electrolytic caps which have say a rating of 3000 hours at maximum operating core temperature and working voltage may last 50000+ hours or more if operated at 1/3 their working voltage and a fraction of their maximum operating core temperature. Of course, this has to be considered on a case by case basis. But, that said, I have serviced vintage communications receivers from the 50s which had electrolytics which were absolutely fine. As stated by JL, a great deal has to do with how much use, and how often they are used; so your technician may be quite correct in telling you that it isn't necessary to replace the electrolytics at this time. Quote Link to comment Share on other sites More sharing options...
tube fanatic Posted July 21, 2011 Share Posted July 21, 2011 I just remembered having this bookmarked. It will shed some light on the electrolytic issue: http://www.niccomp.com/Products/General/Alumlyticlifeexpect.pdf Quote Link to comment Share on other sites More sharing options...
gagelle Posted July 22, 2011 Author Share Posted July 22, 2011 Thanks everyone for the feedback. So refurbishing the whole amp may not be necessary? I hardly have to raise the volume in my small room with KLF-30s. It sounds terrific. The fellow who sold it to me changed some parts that weren't up to specification. He also cleaned out the corrosive glue that Sansui used on this series of amps (AU-717) and replaced everything that came into contact with it. He also told me that when the electrolytics go bad, you usually will hear a hum. The other argument I've read in favor of complete restoration is that technology has changed since the 70s and high quality components are just better than they were. On another Sansui unit, I think I was ripped off but I'm not sure. It makes a low cracking electrical sound from one speaker when I turn it on. The strange thing is that when I turn on a lamp (with a flouresent bulb) that's plugged into the same surge protector, I hear the same sound from the speaker--Very weird. It was also partially restored and tested, by a different technician. It's a 9010 receiver, which is the European version of the 881--same specs just different appearance. I'm going to try it in another room to see if I get the same sound. My apartment was built in the 70s and some of the outlets should probably be replaced. California also lowers the voltage during periods of heavy use in the summer. I bought a power conditioner that should arrive soon. It's a Furman Elite 15i. It was used 3 times at a church function. I paid about $250. Quote Link to comment Share on other sites More sharing options...
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