The 2SC828 is an NPN, Silicon-based AF Amplifier Transistor that is mainly used in AF based audio equipment for amplification and switching. It has a Collector-Emitter Voltage of 25 Vdc with a Collector-Base voltage of 25 Vdc.
This is Boost Module With Digital Display which is a high-performance step-up switching current module. The XL6009 DC-DC 4.5-32V to 5V-35V XL6009 Boost Step-up Module Adjustable Digital Voltmeter.
The 2SK2837, 2SK-2837, K2837, 2837 is a 500V 20A N Channel Silicon Field Effect Transistor Or MOFET TO-3PN-3 Package. Chopper Regulator, DC−DC Converter and Motor Drive.