> The tube holds charge. BIG charge. Compact Macs were dangerous because > of this and I'd assume it's more than a CM on an iMac. > > -Korin > On Tuesday, December 3, 2002, at 09:13 PM, Dean Arthur wrote: > > >> extremely high voltage at the CRT's yoke. > > > > Since when is 15 KV "extremely high voltage?" Rule of thumb is 1 KV per > > diagonal inch of CRT. So a 32-inch viewable screen would require 32 KV > > for deflection.
Horizontal circuit driving both flyback transformer and horizontal beam deflection. Flyback itself generates different voltages, one of voltages sources is HV for the tube via that fat red wire ending in rubber cup. HV is what needed to give electrons a kick towards internal face of CRT's where electrons impacts phorsphours glows. Beam deflection done by magnetic fields generated by two coils made up of yoke placed over the neck against tube's flare, one is horizontal and one for vertical. Yoke doesn't have HV on it except horizontal has spikes of around 1,000 Volts that makes you jerk back if touched exposed horizontal terminals. That high voltage spikes is caused by flyback and horizontal coil magnetic fields collasping violetly generating back voltage spike, occurs with every cycle, frequency is around 15.7khz for NTSC TV, monitors even higher. Vertical is low frequency (60Hz for TV) and low voltage with retrace of around 48V pulse to kick beam from bottom left back up to upper right. Actually for 32" tv it is about 28KV via that red wire to the rubber suction cup on the bell of tube. Projectors usually are in 28 to 30KV range. HV for tubes is very low current but BIG OUCH! The possible secondary injury is flinging one's part of body against something that could cut. The true danger is from the non-isolated main sources and high current flowing around on the mainboard itself that has few amps. This is what kills & hurts real bad and that is reason I prefer that people who don't have famillarity with these type to leave monitors & TVs alone. If you must repair or swap, do it after unplugged overnight and reassemble completely to test. If you must adjust live, use plastic adjusting tools and do it with one hand behind back and make sure someone is present. Don't break that cardinal rule, if you don't feel sightest unsure about it, simply send it out for repair. Cheers, Wizard -- PCI-PowerMacs is sponsored by <http://lowendmac.com/> and... Small Dog Electronics http://www.smalldog.com | Refurbished Drives | -- Sonnet & PowerLogix Upgrades - start at $169 | & CDRWs on Sale! | Support Low End Mac <http://lowendmac.com/lists/support.html> PCI-PowerMacs list info: <http://lowendmac.com/lists/pci-powermacs.shtml> --> 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/pci-powermacs%40mail.maclaunch.com/> Using a Mac? Free email & more at Applelinks! http://www.applelinks.com
