Itron HB 2F89068 Mark III FMCRT  
Written by AnubisTTP on 2011-03-12  



The Itron 2F89068 is a flat matrix cathode ray tube, or FMCRT for short, which was used in 'Junbotron' style large scale video displays. FMCRT cells display images using a series of flood beam CRT electron guns with overlapping X and Y gate electrodes, effectively converting a typical cathode ray tube into a single pixel bitmapped device. The example shown here is a Mark III FMCRT, which differs from earlier FMCRT displays in that it contains a contrast-enhancing magnifier that improves outdoor visibility while allowing for a smaller pixel size. Each tube contains four separate pixels which each contain four individually controllable subpixels. Since the human eye is most sensitive to light in the green band of the electromagnetic spectrum, each pixel contains two green elements in a typical RGGB configuration to enhance the apparent brightness of the display at long distances. Each subpixel can display up to 256 different brightness levels, allowing for millions of possible color combinations. Despite it's smaller size, this display has a longer lifespan than the Futaba device shown above, and is rated for 12,000 hours of use at normal operating voltages.

Mark III FMCRT's were manufactured with three different part prefixes; HB, HG and HR, which each had different pixel dimensions and power requirements. The example shown here is an 'HB' version.


Itron 2F89068 'Mark III' flat matrix CRT, the display element used in Mitsubishi 'Jumbotron' style displays.

This tube is equipped with an external filter and magnifier, which increases the contrast of the display to the level needed for outdoor use.

The 2F89068 is equipped with a plastic base and socket which reins in the side-exiting leads for easy replacement.

Itron HBB Diamondvision Tube
Itron flat matrix CRTs made use of a socket with a gasket to prevent water infiltration in outdoor installations.

Itron Flat Matrix CRT
This HBB4 FMCRT has had its cover removed so the internal structure is visible. The 16 electron guns are visible as round perforations in the back of the tube. The square boxlike plates at the front of the tube are the anode.

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