Q&A - July/August, 2007

TV Half-Life

Q. I read somewhere in your magazine that cathode-ray tube TVs have a half-life of 30,000 hours. At 6 hours a day, that's around 13 years. I'm about to make the HDTV plunge. What are the half-life specs for plasma, LCD, and DLP? Jeff Dorscher Glendale, AZ

A. Al Griffin says: Most plasmas are spec'd for a half-life (the amount of time it takes for the screen to drop to 50% of its original brightness) of 60,000 hours, or twice as long as CRTs. And the half-life spec for LCD TVs is around the same. Most DLP and LCoS (a.k.a. SXRD or D-ILA) TVs, on the other hand, use a replaceable lamp to project images. When the picture starts to look dimmer (usually after 5,000 to 8,000 hours), you simply pop in a new lamp to restore the TV to its original brightness. The exception: LED-driven DLP sets, which have no lamps to replace.

Loopy EQ

Q. I had my graphic equalizer connected to the "pre-main coupler" of my stereo receiver, but that circuit stopped working. Is there another way to hook up the equalizer? Marc Protasel Redondo Beach, CA

A. Ian G. Masters says: Many receivers offer "pre-out" and "main-in" jacks that let you interrupt the signal from the control section (preamplifier) to the power amp to connect equalizers and other components. If none is connected, the jacks are usually bridged by U-shaped metal jumpers. There's really nothing that can break in this arrangement, so your problem may be in the equalizer. Either way, an alternative is to hook up the equalizer to one of the tape monitor loops, and you'll find out quickly if the failure is in the EQ.

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