Guide to Plasma TVs

What you need to know about plasma TVs

Plasma TVs, like LCD and OLED TVs, are a type of flat panel television. Although they both look very similar on the outside, there are big differences on the inside. Learn how plasma TVs work and whether or not they're worth keeping today.

In 2014, Panasonic, Samsung, and LG announced the end of plasma TV production, effectively discontinuing this type of TV. This article is preserved for historical reference.

How Does a Plasma TV Work?

Plasma TV technology is similar to that used in a fluorescent light bulb. The display panel consists of cells, each containing two glass panels that are separated by a narrow gap. Neon-xenon gas is injected and sealed in plasma form during the manufacturing process, and the gas is electrically charged at specific intervals when the plasma set is in use. The charged gas strikes red, green, and blue phosphors, creating a TV image.

Plasma TV technology is different from its immediate predecessor, the traditional cathode ray tube (CRT) TV. A CRT is a large vacuum tube in which an electron beam emanating from a single point in the neck of the tube scans the face of the tube very rapidly. The red, green, or blue phosphors on the tube's surface are then lit up to create an image.

With plasma TVs utilizing a sealed cell with charged plasma for each pixel, the need for a scanning electron beam is eliminated. Thus, there's no need for a large vacuum tube. This is why CRT TVs are shaped more like boxes and plasma TVs are thin and flat.

Plasma TV Technology
Wikimedia Commons – Public Domain

Each group of red, green, and blue phosphors on a plasma TV is called a pixel (picture element).

How Long Do Plasma TVs Last?

Early plasma TVs have a half-life of about 30,000 hours, which means that the image loses approximately 50% of its brightness after 30,000 hours of watching. However, due to technology improvements made over the years, most plasma sets have 60,000-hour lifespans, with some sets rated as high as 100,000 hours.

If a plasma TV has a 30,000-hour rating and is on eight hours a day, its half-life would be about nine years. If on four hours a day, the half-life would be about 18 years. Double these figures for a 60,000-hour half-life. If a plasma TV has a 100,000-hour rating and is on 6 hours a day, its half-life would be about 40 years. Even at 24 hours a day, a 100,000-hour half-life is about 10 years.

For comparison, a CRT TV loses about 30% of its brightness after about 20,000 hours. Since this process is very gradual, most viewers aren't aware of this effect, although they may need to periodically adjust the brightness and contrast controls to compensate. Just as with any TV technology, display lifespan can also be affected by environmental variables, such as heat and humidity.

Do Plasma TVs Leak?

The gas in a plasma TV does not leak, nor can more gas can be pumped in. Each pixel element is a completely sealed structure (referred to as a cell), which includes a phosphor, charging plates, and plasma gas. If a cell fails, it can't be repaired by recharging the gas. If a large number of cells go dark, then the entire panel needs to be replaced.

Can a Plasma TV Work at High Altitudes?

Most plasma TVs are calibrated for optimum operation at, or near, sea-level conditions. Since the pixel elements on a plasma TV are glass housings containing rare gases, thinner air causes greater stress on the gases inside the housing.

As altitude increases, plasma TVs need to work harder in order to compensate for the difference in external air pressure. As a result, the set will generate more heat, and its cooling fans (if it has them) will work harder. This may cause a buzzing sound. In addition, the half-life of the plasma TV will be reduced somewhat.

For most consumers, this is not an issue, but there are considerations if you live in an area over 4,000 feet above sea level. Some plasma TVs are robust enough to work well at altitudes of up to 5000 feet or more. There are high altitude versions of some plasma TVs that can hold up to as high as 8,000 ft.

Do Plasma TVs Generate Heat?

Since plasma TVs use charged gas, the set will be warm to the touch after being in operation for a while. Since most plasma TVs are wall or stand mounted, heat generation is usually not an issue with plenty of air circulation. However, plasma TVs use more energy than a standard CRT or LCD set.

Avoid placing a plasma TV in a tight space where it won't have enough room to dissipate the heat that it generates.

What Is a Sub-Field Drive on a Plasma TV?

In order to display smooth images, TVs employ refresh rates and motion processing. LCD and plasma TVs typically have a 60hz refresh rate, but that is not always enough. To enhance motion response, plasma TVs employ additional technology called a Sub-Field Drive.

Plasma TV Sub-field Drive Example
Images courtesy of Amazon.com

Many TV buyers think that the sub-field drive rate is comparable to the screen refresh rates used in LCD TVs. However, the sub-field drive rate on plasma TVs works differently.

Are All Plasma TVs HDTVs?

In order for a TV to be classified as an HDTV or HDTV-ready, it must be able to display at least 1024x768 pixels. While some plasma TVs meet the requirements for HD, there are no plasma TVs that display 4K resolution with the exception of very large screen units made for commercial use only.

Some early model plasma TVs only display 852x480. These sets are referred to as EDTVs (Extended or Enhanced Definition TVs) or ED-plasmas. ED resolutions are fine for DVDs and standard digital cable, but not for HD sources. Plasma TVs that are capable of displaying HDTV signals accurately have a pixel resolution of at least 1280x720 (720p) or higher.

Some manufacturers labeled their 1024x768 plasma TVs as EDTVs or ED-plasmas, while others labeled them as plasma HDTVs. This is where looking at specifications is important. If you are looking for a true HD-capable plasma TV, check for a pixel resolution of either 720p or 1080p.

Plasma TVs and Scaling

Since plasma TVs have a finite number of pixels, higher resolution input signals must be scaled to fit the pixel field count of the particular plasma display. An HDTV input format of 1080p needs a display of 1920x1080 pixels for a one-to-one pixel display of the HDTV image.

If a plasma TV only has a pixel field of 1024x768, the original HDTV signal must be scaled to fit that pixel count. So, even if your plasma TV is advertised as an HDTV with a 1024x768 pixel screen, HDTV signal inputs will be scaled down. If you have an EDTV with 852x480 resolution, any HDTV signals will have to be scaled down.

The resolution of the image viewed on the screen does not always correspond to the resolution of the original input signal.

Will a Plasma TV Work With an Old VCR?

All consumer plasma TVs will work with any existing video device with standard AV, component video, or HDMI outputs. Since VHS is of such low resolution and has poor color consistency, it will not look as good on a large plasma screen as it does on a smaller 27-inch TV. To get the most out of your plasma TV, use a Blu-ray disc player or an upscaling DVD player.

What Else Do You Need To Use A Plasma TV?

Here are some tips on what you need to budget for in addition to your plasma TV in order to use it to its full potential:

  • A surge protector.
  • A sound system. Although some plasma TVs have an internal sound system, it is best to connect it to a soundbar or a home theater receiver.
  • Connection cables to connect your plasma TV with your other components.
  • Source components (Blu-ray players, video game consoles, satellite or cable boxes, media streamers, etc.)

Should You Keep Your Plasma TV?

If your plasma TV still works fine for you, there's no reason to throw it out. However, you could vastly improve your viewing experience by upgrading to a newer type of television.

Since plasma TVs have been discontinued, TV makers have introduced newer technologies such as 4K displays, HDR, Wide Color Gamut, and Quantum Dots (sometimes referred to as QLED) into OLED and LCD TVs. Before you buy a new TV, compare all types and sizes that are available in order to see what will work best for you.