it may have some ac on it. getting zeners in that voltage range is no problem, they're generally available up to about 200v. the thing is neon lamps are incredibly cheap and very, very robust in case of a huge surge. neon lamps also don't just limit the voltage to 60 or 70 volts when they come on, they become almost a short circuit and quickly reduce the voltage to almost nothing and tend to latch on until power is interrupted, both of which can be useful. a zener by contrast leaves the voltage at a certain voltage, which can mean dissipating allot more power, since power is V X I, whereas the zener drops the voltage way down and doesn't have to keep dissipating allot of power. also it is useful to an extent to be able to see the lamp come on, but that's more of an extra bonus. also, if a zener fails, it may fail open or shorted, if a neon fails it will almost certainly be shorted or the glass envelope will pop from excessive temperatures.
Jeff Walther wrote: ------- > Thank you, Philip. That makes a lot of sense. Any idea why they > don't use a Zener Diode for this? Too hard to get a high enough > breakdown voltage or can't handle enough power? Or this is an AC > circuit and it wouldn't work there... ------ -- "To preserve liberty, it is essential that the whole body of the people always possess arms, and be taught alike, especially when young, how to use them." (Richard Henry Lee, Virginia delegate to the Continental Congress, initiator of the Declaration of Independence, and member of the first Senate, which passed the Bill of Rights.) -- Compact Macs is sponsored by <http://lowendmac.com/>. Support Low End Mac <http://lowendmac.com/lists/support.html> Compact Macs list info: <http://lowendmac.com/lists/compact.shtml> The FAQ: <http://macfaq.org/> --> AOL users, remove "mailto:"; Send list messages to: <mailto:[EMAIL PROTECTED]> To unsubscribe, email: <mailto:[EMAIL PROTECTED]> For digest mode, email: <mailto:[EMAIL PROTECTED]> Subscription questions: <mailto:[EMAIL PROTECTED]> Archive:<http://www.mail-archive.com/compact.macs%40mail.maclaunch.com/> Using a Mac? Free email & more at Applelinks! http://www.applelinks.com
