The **FBK-R** (often referred to as the FBK-R series) typically refers to a specialized line of **High-Voltage Resistors** and **Focus/Screen Resistor Blocks** used primarily in CRT (Cathode Ray Tube) televisions, monitors, and specific high-voltage power supply units. These components are critical for managing the high potential required to accelerate electrons and provide focus voltage to the display. --- ### 1. Key Electronic Components and Composition The FBK-R is not a single simple resistor but a composite electronic module. Below are the internal parts and materials: | Part Name | Material/Composition | Function | | :--- | :--- | :--- | | **Resistive Element** | Thick Film Cermet / Metal Oxide | Provides high resistance (usually in Giga-ohms) to step down high voltage. | | **Substrate** | High-purity Alumina (Ceramic) | Acts as a heat-dissipating, non-conductive base for the resistive ink. | | **Adjustment Knobs** | Potentiometers | Integrated "Focus" and "Screen" (G2) controls for manual calibration. | | **Encapsulation** | Epoxy Resin / Silicone | Provides insulation and protects against high-voltage arcing and moisture. | | **Lead Wires** | High-Voltage Silicone Wire | Connects the block to the Flyback Transformer (FBT) and the CRT socket. | --- ### 2. Functional Specification The FBK-R acts as a **Voltage Divider**. It takes the high-voltage output from the Flyback Transformer (typically 20kV - 30kV) and divides it into two primary signals: 1. **Focus Voltage (Vf):** Usually between 5kV and 10kV. It adjusts the sharpness of the electron beam. 2. **Screen Voltage (Vs):** Also known as G2 voltage, typically between 200V and 1000V. It controls the overall brightness/cutoff level of the display. --- ### 3. Technical Characteristics In electronic design, FBK-R parts are selected based on the following parameters: * **Resistance Tolerance:** Usually ±10% to ±20% due to the high-voltage nature. * **Voltage Coefficient:** Extremely low to ensure resistance remains stable even as voltage fluctuates. * **Dielectric Strength:** Designed to withstand atmospheric pressure changes without "leaking" electricity (arcing). * **Safety Rating:** Often includes flame-retardant coating (UL94V-0) to prevent fires in case of component failure. --- ### 4. Common Failure Modes Due to the high stress placed on these parts, they may experience: * **Internal Arcing:** Visible or audible "snapping" inside the block when the insulation breaks down. * **Drift:** The resistance value changes over time, causing the screen image to become blurry (Focus drift) or change brightness (Screen drift). * **Potentiometer Wear:** The physical wipers inside the adjustment knobs can oxidize, leading to "flickering" settings. ---