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NotTaR of Television Sets : Horizontal output transistor pinouts    
 Copyright © 1994-2007, Samuel M. Goldwasser. All Rights Reserved. Reproduction of this document in whole or in part is permitted if both of the following conditions are satisfied: 1. This notice is included in its entirety at the beginning. 2. There is no charge except to cover the costs of copying. I may be contacted via the Sci.Electronics.Repair FAQ (www.repairfaq.org) Email Links Page.
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Horizontal output transistor pinouts

You will nearly always find one of two types of horizontal output transistors in TVs and monitors:

  • Metal can - TO3 package: 
                  _
            / O \         View from bottom (pin side)
          / o   o \
         (  B   E  )      B = Base, E = Emitter, C = Collector
          \       /
            \ O / C       The metal case is the Collector.

  • Plastic tab - TO3Pn (n = several suffixes) package: 

                _____
           /     \
          |   O   |      View from front (label side)
          |       |
          |       |      B = Base, E = Emitter, C = Collector
          |_______|
            | | |        If there is an exposed metal tab, this is the
            | | |         Collector as well.
            B C E

    Some other transistor types use the same pinout (TO66 for metal can, TO218 and TO220 for plastic tab) but not all. However, for horizontal output transistors, these pinouts shouuld be valid.

    Note that those with a built in damper diode may read around 50 ohms between B and E (near 0 on the diode test range) - this is normal as long as the resistance is not really low like under 10 ohms.

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