OTHER TECH

Mysterious Hum

Q. My bedroom audio system is made up of an old, high-quality mono radio that has a line-level output for a matching powered speaker for stereo. Recently, I've been getting a hum from the main radio section (but not the powered satellite). It starts off very low and rises until the speakers pop, and the whole thing starts all over again. If I touch the radio's outer housing, it interrupts the cycle with a loud static sound. I tried replacing the power strip the unit is plugged into, but the hum eventually returned. The system was a gift to my wife and has sentimental value to us, so I'd like to fix it. Any idea how? Harold Bonet BRONX, NY

A. Ian G. Masters says: It doesn't sound like a grounding problem. The gradual buildup suggests a malfunctioning capacitor, which gradually acquires a charge that inhibits its ability to filter out the 60-Hz line frequency (the hum), until it suddenly discharges with a pop, returning the circuit to normal for a moment, then starting the process over. Your touching the cabinet hastens the discharge, with the same result. It's most likely in the amplifier section of the main radio, since it doesn't affect the satellite. I don't imagine a qualified technician would have much trouble dealing with this, as long as he's willing to take on an older piece of gear.

Frame-Rate Agility

Q. I read that the new Pioneer TVs will display at both 60 and 72 frames per second (fps), using the latter frame rate to avoid 2:3 pulldown (and associated artifacts) for film-based (24 fps) programming. Are there other TVs that are frame-rate agile? Chris Llana CHAPEL HILL, NC

A. Al Griffin says: Pioneer plasmas with the company's Advanced PureCinema II processing can convert 60-Hz signals with 2:3 pulldown to 72-Hz with a 3:3 cadence. This eliminates the slight staggering of motion that occurs when film, with its 24-frame-per-second rate, is converted to 30- or 60-fps video. The process works with any standard video source, such as DVD or broadcast. In addition, the new top-of-the-line Pioneer plasmas have the capability of accepting 1080p/24-fps signals and converting them directly to 72 Hz by tripling the signal's frame rate (24 x 3 = 72). Taking advantage of this new feature element requires a video source capable of putting out a 1080p/24-fps signal, however, and the only ones that I know of are forthcoming Blu-ray players from Pioneer and Sony. Are frame rate-flexible HDTVs the wave of the future? Companies like Philips and, more recently, JVC have developed HDTVs that show video at higher-than-average refresh rates, but these sets weren't necessarily designed for a 24-fps input signal, so the exact benefit of the higher refresh frequency depends on how the signal is processed to take advantage of it. With new high-def disc players that put out native 24-fps video hitting the streets, however, we're likely to see greater input flexibility on future HDTVs.