This part is a kind of semiconductor called BU4508DX.

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 BU4508DX DESCRIPTION ·Collector-Emitter Sustaining Voltage- : VCEO(SUS)= 800V (Min) ·High Switching Speed ·Built-in Damper Diode APPLICATIONS ·Designed for use in horizontal deflection circuits of color TV receivers. ABSOLUTE MAXIMUM RATINGS(Ta=25℃) SYMBOL PARAMETER VALUE UNIT VCES Collector- Emitter Voltage(VBE= 0) 1500 V VCEO Collector-Emitter Voltage 800 V VEBO Emitter-Base Voltage 8V IC Collector Current- Continuous 8A ICM Collector Current-Peak 15 A IB Base Current- Continuous 4A IBM Base Current-Peak PC Collector Power Dissipation @ TC=25℃ TJ Junction Temperature Tstg Storage Temperature Range 6A 45 W 150 ℃ -65~150 ℃ SYMBOL PARAMETER MAX UNIT Rth j-c Therm [ ... ]

BU4508DX PDF Datasheet Download