How to Activate a Horizontal Output Transistor

CRT technology has been largely replaced by LCD and plasma HDTVs.

A cathode ray tube, or CRT, is a type of television monitor that uses a large glass tube and electron gun to stimulate a screen of phosphors and reproduce an image. CRT monitors paint the phosphor screen by steering a high-voltage beam of electrons in a zigzag pattern, from the top of the screen to the bottom, from left to right. A high-voltage flyback transformer generates the voltages required to rapidly pull the electron beam from the far-right to the far-left, after an entire horizontal row has been drawn. A horizontal output transistor, or HOT, drives the flyback transformer.

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CRT horizontal driver and transformer
CRT horizontal output transformer
Soldering iron and solder
18-gauge or larger wire

Instructions

- 1
  
  Plug in the soldering iron and allow it to warm up. This should take about one minute.
- 2
  
  Locate the horizontal driver and transformer. This circuit provides the high current necessary to drive the horizontal output transistor.
- 3
  
  Connect one end of the wire to the output of the horizontal driver and transformer. Overlap a piece of solder onto the wire and touch it with the hot tip of the soldering iron. The solder instantly melts and joins the wire to the horizontal driver and transformer.
- 4
  
  Connect the other end of the wire to the base of the horizontal output transistor. Solder it using the same technique as the previous step. The horizontal output transformer is now connected to the horizontal driver and transformer. When power is applied to the driver, the horizontal output transformer is activated, providing the high-speed switching required to properly run the flyback transformer.

Tips & Warnings

If your horizontal output transistor is connected to a flyback transformer, then you must discharge it before working on the circuits. The flyback transformer can carry a large amount of electrical charge even after it has been disconnected from power. This poses a significant shock hazard. See "Resources" for more information on this.

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