This post explains for the transistor.
The Part Number is BLD128D.
The function of this semiconductor is 400V, 5A, NPN Transistor.
The package is TO-220 Type
Manufacturer: SI Semiconductors
This is Silicon NPN transistor in a TO-220 Plastic Package.
1. High voltage capability, high speed switching, wide SOA,ROHS compliant
Absolute maximum ratings ( Ta=25°C )
1. Collector to Base Voltage: Vcbo = 700 V
2. Collector to Emitter Voltage: Vceo = 400 V
3. Emitter to Base Voltage: Vebo = 9 V
4. Collector Current: Ic = 5 A
5. Collector Dissipation : Pc = 2W
6. Junction Temperature: Tj = 150°C
7. Storage Temperature: Tsg = -55 ~ +150°C
Fluorescent lamp, electronics ballast, electronic transformer, switch mode power supply .