This service manual provides service instructions for STB model HD-4001 which uses the V26K chassis. Service personnel should read this manual thoroughly before servicing these chassis. This service manual includes: 1. Safety Precautions 2. Assembly and disassembly instructions. 3. Servicing printed circuit boards (PCBs). 4. Electrical adjustments. 5. Chip parts replacement procedures. 6. Circuit path diagrams. The parts list section of this service manual includes: 1. Cabinet and screen parts. 2. Electrical parts. Schematic and block diagrams of the above listed models are included in this service manual for better understanding of the circuitry. PCB drawings are also included for easy location of parts and test points.