CRT service safety — What should you do first before discharging a CRT display?

Introduction / Context:
CRT displays retain high voltage even after shutdown, presenting serious shock hazards. Proper discharge procedure begins with ensuring all power sources are removed and the technician follows safe handling steps.

Given Data / Assumptions:

• A conventional CRT monitor or TV set with an anode cap and flyback transformer.
• Technician intends to discharge the CRT safely.
• Appropriate discharge tools (insulated HV probe with bleeder resistor) are available.

Concept / Approach:

Before interacting with any high-voltage section, eliminate live power to prevent additional charging and to reduce the risk of accidental energization. Only then proceed with discharge using the manufacturer-recommended method.

Step-by-Step Solution:

Verification / Alternative check:

Service manuals universally start with “disconnect power” in their safety sections. Only after this step is the anode discharge procedure performed.

Why Other Options Are Wrong:

Removing housings or boards while still connected increases risk. Disconnecting only the signal cable does nothing for high voltage. “None of the above” is incorrect because removing power first is the essential step.

Common Pitfalls:

Using a screwdriver to short the anode to ground directly (damaging and dangerous), neglecting eye protection, and working one-hand-in-pocket to reduce current path across the chest.

Final Answer:

Turn the power off and remove the power source (unplug) before proceeding.