Futaba TL-3508XA 'Jumbotron' Display 
Written by AnubisTTP on 2010-03-11  


Back in the time before LEDs, large outdoor displays like the 'Jumbotrons' seen in many stadiums had to rely on tube technology for their displays. The Futaba TL-3508XA flood beam CRT shown here is a rare example of this quite unusual technology. The flood beam CRT differs from a normal CRT in that the electron gun within does not produce a focused controllable beam. Instead, electrons are sprayed in a wide cone across the entire front of the phosphor screen, effectively turning an image display device into a simple light bulb. The TL-3508XA actually contains multiple flood beam devices in a single envelope, enough to display eight pixels of RGB data. A control grid sits in front of each electron gun, allowing the intensity of each pixel to be varied by a low voltage control signal. Thousands of tubes such as this are required to build an entire Jumbotron display.

Tubes were assembled into modules like the Sony A-6279-869-A, which had quick-connect fittings for easy removal. Tubes such as this only had an operational lifespan of around 8000 hours, a means to quickly replace and remove dead display elements was mandatory. The A-6279-869-A modules are equipped with plastic shade bars to increase the contrast of the display.


Futaba TL-3508XA multi-element flood beam CRT, used in 'Jumbotron' outdoor television screens.

The TL-3508XA contains eight pixels, each with three different phosphor segments. Each segment has it's own electron gun and control grid.

Red segments are smaller and placed between blue and green phosphor regions to prevent banding in the displayed image.

TL-3508XA, rear view. The electrode structure is clearly visible through the back of the tube.

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