On Aug 1, 2013, at 10:51 PM, Geoff Oltmans wrote: > I was under the impression that although tantalum caps are good in most > respects they aren't so good at dealing with high ripple currents which can > lead them to fail spectacularly which is one reason that electrolytics are > favored in power supplies.
Actually, the opposite is true. Aluminum electrolytic capacitors have a higher esr (equivalent series resistance) which generates more heat when dealing with ripple current (ceramic capacitors have an even lower esr which is what makes them so good as bypass caps for ICs). Their ability to dissipate heat does not offset the additional heat generation. Additionally, the increase in heat in an electrolytic will also cause the capacitance value to change much more than a tantalum capacitors change with temperature. While you can purchase low esr electrolytic capacitors, they are more expensive and I seriously doubt they saw use on the circuit boards of vintage Macintosh computers (though I can see them having been used in power supplies). In theory a solid tantalum capacitor has an unlimited life and should work just about as well in 50 years as it does today. In most of my designs just about anywhere there was an electrolytic, there was a ceramic and a tantalum in parallel to help compensate for the major shortcomings of the electrolytic. In fact, outside of power supplies, we used very few electrolytics. However, I was involved in industrial and not consumer products so reliability was a greater concern than saving a dollar or two on the cost of product. Derek -- -- ----- 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 vintage-macs@googlegroups.com To leave this group, send email to vintage-macs+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/vintage-macs Support for older Macs: http://lowendmac.com/services/ --- You received this message because you are subscribed to the Google Groups "Vintage Macs" group. To unsubscribe from this group and stop receiving emails from it, send an email to vintage-macs+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
