On Dec 30 2012, 12:26 am, James Fraser <wheresthatistanbul- [email protected]> wrote: > Hello, > > --- On Sat, 12/29/12, Doug McNutt <[email protected]> wrote: > > > And while I'm at it, Apple's choice of aluminum > > electrolytics seems to have used a lot of caps rated at 16 > > volts where a 6 volt rating would be good enough. It's > > likely a perceived saving in parts where variety makes > > automated assembly more difficult. > > > Six volt tantalums are cheaper and smaller if you can > > separate the 12 volt bus from the 5 volt bus. > > I'll bite: when you say "cheaper," are you talking on an industrial scale > (like Apple would use) or on a (typical) hobbyist's scale?
One of the members of 68kmla.org dug up an old white paper on capacitors and expected life times and such and the paper concluded that capacitor's have much longer lives if they are never operated close to their actual voltage rating. The paper or a link is posted somewhere in the forums over there. I didn't keep a link, so to find it you'd have to search. I think JDW may have posted it, but I'm not certain. If you actually look at the expected hours rating on some of the electrolytics, it is as low as 1000 hours. Even in a home environment, that time would be consumed quickly and in an office environment the capacitors would not last out the year. The paper recommended voltage ratings approximately three times the expected operating voltages. So, in a 5V circuit, 16V is just about perfect. The 1uF 50V capacitors Apple was so fond of are a little odd, given that they're probably in, at most, a 12V circuit, so for those I have a 1uF, 35V cap. as the 50V variety was difficult to find in the small package size (physical envelop) needed. So, while it would seem that one would use 6V capacitors in a 5V circuit, according to some evidence some of us read once, 16V is a much better choice. :-) > I ask because, just out of curiosity, I pulled up an old post that listed the > caps that Jeff Walther was offering a couple of years back (NB: circa 2010; > he may or may not be offering the same selection in 2012) and didn't see > any caps with less than a 16V rating: The selection has changed slightly and some new stuff has been added, but it's still basically the same. My posting is sticky'd in the "Trading Post" forum on 68kmla. I wish I had time to do capacitor installations too, but I just don't. I have a job, a house, a 10-year-old son, fish, a vegetable garden, I coach LL baseball two seasons a year, and I have an anemic thing resembling a social life as well... Jeff Walther -- ----- You received this message because you are a member of the Vintage Macs group. The list FAQ is at http://lowendmac.com/lists/vintagemacs.shtml and our netiquette guide is at http://www.lowendmac.com/lists/netiquette.shtml To post to this group, send email to [email protected] To leave this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/vintage-macs Support for older Macs: http://lowendmac.com/services/
