IMPORTANT: CRT MONITORS CAN HOLD ANYWHERE BETWEEN 15K VOLTS (small B&W)-25k VOLTS (small-medium color), UP TO 50K (TVs, studio monitors, high-end desktop monitors like the GDM-FW900). DUE TO THE WIDE VARIATIONS OF WHAT EACH TYPE CAN HOLD IT IS CRITICAL THESE GET DISCHARGED CORRECTLY!
Sources used:
This Wiki intends to bridge the information from this answer made in 2018 and expand on this topic further, and make the format better suited to be used in the field. This post was made as the age of the answer most of this information was in has aged to a point it is hard to locate: Disassembling an old Apple monitor. In addition to this answer and post, refer to this Apple document: CRT Safety.
How to discharge a CRT
The first rule to safely discharge a CRT monitor is to ensure the monitor or computer is unplugged to prevent further charge from coming back. In addition, IF possible, flip the power switch on for 30 seconds, up to 1 minute (or hold the power button) to discharge the monitor. On a modern "bleeder-based" CRT, this may be enough to work on it safely, but beware: These resistors are typically burned out or abused and may not work well (or do their intended job) today! This is especially true since the draining process with the resistor-based tubes is "silent" and will not provide a visual indication, so a manual discharge is still a requirement.
Key takeaway: DUE TO THE ABUSE THESE RESISTORS TOOK WHEN THE CRT DISPLAY WAS NEW OVER THE COURSE OF TIME WHEN THE CRT DISPLAY WAS YOUNG, ASSUME THEY ARE BURNED OUT WITH THE AGE OF THESE MONITORS TODAY!
IMPORTANT: DO NOT WEAR ANY GROUNDING STRAPS; ELECTRICITY CHOOSES THE PATH OF LEAST RESISTANCE AND YOUR ESD PROTECTION WILL BECOME THE GROUND. As such, you must remove all jewelry (and items like necklaces or chokers with a metal clasp; yes, that clasp is enough to get you) to mitigate the risks with jewelry completely.
CRT discharge tool
After making sure you do not become the new "ground," it is time to discharge the CRT. You can do this with an official discharge tool (these were made for companies like Apple for service purposes) or an open-market tool when they were available and sold to the public (or at least, only to third-party repair shops).
NOTE: These tools are no longer in production and are extremely rare (if not unobtainable today). As such, we now need to improvise; you can use a plastic-handled screwdriver with a rubber grip as a discharge tool. However, a rubber coated handle is strongly recommended (and use of such a screwdriver is encouraged). The risk of injury or death greatly outweighs the slight markup to have a rubber insulated handle as an additional safety layer.
These are not hard to find and can readily be found in hardware stores such as Home Depot or Lowes. These can sometimes cost significantly more than a plastic handle driver but are properly insulated.
If possible, it is also advisable to insulate part of the screwdriver handle with heat-shrink tubing; this provides an additional cushion in case you touch the metal on the screwdriver. Caution is still required. Refer to this guide for a visual aid on the discharge process: Macintosh Classic II Power Board Removal
If you can locate the tool, this is generally what they look like (this tool is an example of the Apple-made version before they stopped working on CRT based Macs). However, other versions were also made by different companies that serve the same purpose:
IMPORTANT: WHEN DISCHARGING THE CRT ITSELF, DO NOT HAVE BOTH HANDS IN THE WORKSPACE! IF BOTH HANDS ARE IN THE SPACE, THIS CAN CREATE A DIRECT SHOCK TO YOUR HEART, WHICH CAN KILL YOU. Put your nondominant hand behind your back or a pocket to make sure you do not create a complete circuit and use your preferred dominant hand.
Key takeaway: It is better to drop a loud F-bomb your neighbor can hear with one hand in your pocket instead of being dead... Once you hear the CRT make a "crack" sound, the CRT has been discharged.
If you have followed these safety rules to a T, you have successfully discharged a CRT and did not injure or shock yourself while discharging your CRT display.
2 Yorum
Thank you so much! very helpful!
Michael Callahan - Yanıt
Important Safety Reminder – Read Before Proceeding
Before attempting to discharge a CRT, make sure you’re not alone. Always have another person in the room while performing this procedure in case something goes wrong. CRT discharges involve lethal voltages, and although injuries are rare when done properly, accidents can happen—especially if you’re startled or working in an unfamiliar environment.
Also:
• Remove all jewelry (rings, bracelets, watches, necklaces). Metal conducts electricity and can cause severe burns or even arc in the presence of high voltage.
• Avoid clothing that builds static (like synthetic fleece, wool, or polyester). Stick to 100% cotton if possible.
• Work on a non-conductive surface, in a dry, well-lit environment.
Respect the danger, work carefully, and you’ll be fine—but having a second person nearby is not just smart, it’s potentially life-saving.
nirv - Yanıt