This part is a kind of semiconductor called MD1803DFX.

Function of this product has Silicon NPN Power Transistor.

Manufacturers : Inchange Semiconductor

Image and pinout :

Some of the text within the PDF file :

INCHANGE Semiconductor isc Silicon NPN Power Transistor isc Product Specification MD1803DFX DESCRIPTION · High Voltage · Low base-drive requirements · Collector-Emitter Sustaining Voltage- : VCEO(SUS)= 700V (Min) APPLICATIONS ·Horizontal deflection output for TV ABSOLUTE MAXIMUM RATINGS(Ta=25℃) SYMBOL PARAMETER VALUE UNIT VCBO Collector-Base Voltage 1500 V VCEO Collector-Emitter Voltage 700 V VEBO Emitter-Base Voltage 10 V IC Collector Current- Continuous 10 A ICM Collector peak current (tp<5ms) 15 A IB Base Current- Continuous 5A PTOT Total dissipation at TC=25℃ 57 W TJ Junction Temperature 150 ℃ Tstg Storage Temperature Range -65~150 ℃ THERMAL CHARACTERISTICS SYMBOL PARAMETER Rth j-c Thermal Resistance,Junction to Case MAX 2.2 UNIT ℃/ [ ... ]

MD1803DFX PDF Datasheet Download