Hear that? Everyone has been forced to endure a buzzing TV at some point in his or her life. Either at the cabin because you’re lucky any signal makes it that deep into the wilderness, or at home with a perfect home-theater setup that insists on mimicking honey bees no matter what you do to stop the annoying hum. In order to keep technical difficulties from ruining your upcoming Super Bowl party (and all your future TV-watching), we decided to equip readers with the knowhow to diagnose and fix their TV when it sounds like an electric toothbrush. Surprisingly, the most common causes for a buzz in your TV have relatively simple cures. There are three prominent problems that can cause your TV to buzz or hum and each is accompanied by a distinct set of sounds and symptoms. These issues are CRT scanning, the infamous “ground loop,” or just plain overmodulation—which sounds more complicated than it is.
This is the least likely cause for TV buzzing, but also the easiest to identify and solve. If your TV was purchased before 2005, there’s about an 80% chance that it’s a cathode ray tube (CRT) model. These are typically massive, clunky, and absurdly heavy televisions that loom ominously in the corner of your grandparent’s house. The hum from these TVs is caused by the scanning frequency the tubes use as they shoot electrons at the screen. The frequency this happens at lies near the upper range of human hearing. This high-pitched tone is inaudible to some, but for those of us used to LCD displays and flatscreens, the whine of a CRT is an annoying relic of the past. Solution: Buy a newer TV or get less good at hearing.
The Ground Loop
The Ground loop is caused by the difference in electrical potential between different grounding points. A ground loop typically produces a loud, low frequency buzz when you plug in audio or video components. If your whole setup is connected, the sound will be constant while power is running to the system and won’t vary based on the images your TV is displaying (an important distinction between ground loops and overmodulation). Here’s a troubleshooting procedure to determine what the cause of your ground loop is and what you can do about it:
- The main culprits are your subwoofer and cable or the satellite box feed at the entrance to your system. Unplug the coaxial cable connected to your subwoofer and determine if the buzz vanishes. If it does, the ground loop is probably coming in through your cable/satellite feed.
- Reconnect the subwoofer from its input to the receiver’s output and disconnect the offending feed from the outboard box or tuner (disconnect the cable before any splitters).
- If the hum disappears, the solution is to install an in-line ground isolator. One issue to consider is that transformer-based isolators are universally compatible with analog feeds, but may interfere with HDTV signals. Check reviews before making your purchase to ensure that your system is compatible.
- If the buzz remains even after you’ve disconnected the TV, you’ll need a ground isolator between the subwoofer and your A/V receiver.
- Finally, you can test these other procedures if you don’t have access to a ground isolator:
- Plug the subwoofer into a separate outlet from the rest of your setup.
- Reverse the AC plug for your A/V receiver or subwoofer (If this plug is a 3-wire plug, you won’t be able to reverse it).
- Connect the chassis screws on your sub and receiver with 14-gauge wire and then unscrew the ground loop screw on the back of your subwoofer.
Overmodulation is a painfully difficult process to translate accurately from telecommunication jargon into layman’s terms. A crude analogy is that overmodulation is like dumping 5 gallons of water into a single measuring cup—the force of the water getting dumped into the cup exceeds the cup’s ability to contain the fluid. When the video signal being sent to a TV is too strong, it causes distortions in the information being transmitted that manifest in a low buzz of about 60hz. The buzz varies in intensity based upon the onscreen graphics because the sharp edges of a figure correspond to drastic contrasts in signal strength. When the signal is too strong, it overpowers your cable box or satellite tuner. Despite the techy explanation, overmodulation is fairly simple to overcome and is common with analog TVs receiving digital signals. First, if you’re using a satellite tuner or cable box, each comes equipped with a “modulator.” If it is poorly manufactured or adjusted incorrectly, it will be the source of your buzzing. Placing and attenuator between your box/tuner and the TV will reduce the signal strength that interacts with the TV receiver. If this doesn’t work, you should get your box/tuner replaced by your cable or satellite provider. If, in the end, none of the above tips help, then your buzzing is likely the cause of an internal problem inside your TV, which requires appliance-repair savvy. Barring that remote possibility, happy viewing.
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