Repairing a CRT TV is often an exciting yet challenging task, especially when it comes to the high-voltage package — a critical component that's prone to wear and tear. Sometimes, parts aren't available, but giving up isn't always the answer. With some knowledge and courage, you can still bring your old TV back to life. The high-voltage package is not just a simple part; it plays a crucial role in generating the high voltage needed for the cathode ray tube to function properly.
First, let’s understand the function of the high-voltage package. Also known as the line output transformer, it's responsible for generating the anode high voltage (HV), which powers the screen. It also provides focus (FV) and acceleration (SV) voltages. However, it's important to note that the deflection current isn’t supplied by the high-voltage package but by the S-correction capacitor. When the line transistor turns off, the B+ voltage charges the S capacitor through the high-voltage package and the deflection coil, with the current passing through the package. Due to its operation under high temperature, high frequency, high voltage, and large current conditions, along with exposure to moisture or dust, the high-voltage package is highly susceptible to failure.
Second, common issues that can damage the high-voltage package include:
- Breakdown of the high-voltage filter capacitor inside the package.
- Short circuits between the high-voltage coils.
- Leakage or breakdown of the high-voltage silicon rectifier.
- Short circuit between the primary and secondary coils.
- Aging components leading to unstable focus and acceleration voltages.
- Reduced insulation causing internal or external arcing.
Third, here are some key terms related to the high-voltage package:
1. **HV (Anode High Voltage)** – Typically ranges from 23KV to 29KV depending on the picture tube size.
2. **FV (Focus Voltage)** – Usually obtained via a resistor potentiometer at the HV terminal, ranging from 3KV to 10KV.
3. **SV (Acceleration Voltage)** – Also known as G2, usually around 150V to 1000V.
4. **AFC (Automatic Frequency Control)** – Refers to the synchronization signal used by the scan chip and CPU.
5. **ABL (Automatic Brightness Control)** – Monitors the high-voltage current and limits brightness if necessary.
6. **Primary and Secondary Windings** – The primary has fewer turns and is less likely to fail, while the secondary has many small turns and is more prone to short circuits.
7. **Inductance** – The property of a coil that opposes changes in current, measured in millihenries (mH).
8. **Forward and Reverse** – Refers to the scanning direction of the electron beam.
9. **Forward and Reverse Rectification** – Different rectification methods yield different voltage levels.
10. **Winding Polarity** – Important for proper voltage output and must be considered when rewinding.
11. **Field Power Supply & AFC Adjustment** – Can be adjusted using self-wound coils when replacements are unavailable.
12. **Pin Function Check** – Always verify connections before powering on the device.
For reference, here are some common high-voltage package data files:
High pressure package information.pdf
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