Editing CRT Discharge Procedure

[[File:Schneider-MM12-Monochrome-Monitor-Open-3.jpg|thumb|340x340px|CRT Inside a MM12 Monitor]]
Cathode Ray Tubes (CRTs), used in vintage Macintosh and other classic computers, can '''retain a dangerous high voltage charge for hours or even days''' after being powered off. To avoid '''electric shock or injury''', proper discharge is essential before performing internal repairs.

== ⚠️ Safety Warning ==

Working with CRTs involves potentially lethal voltages ('''up to 25,000 volts'''). '''It will kill you if you don't safely discharge it'''. You should '''only discharge a CRT''' if you are confident and equipped to do so safely.

=== Minimum Safety Precautions ===
* Unplug the system and wait at least 30 minutes before starting.
* Use only '''insulated tools''' and wear '''rubber-soled shoes'''.
* Never work on a CRT in a damp or conductive environment.
* Discharge the CRT before touching or removing the analog board.

== Tools Required ==

To safely discharge a CRT, you will need:

* '''Flat-head screwdriver''' – Preferably with a long, insulated handle.
* '''Alligator clip jumper wire''' – To ground the tool.
* '''Gloves''' – High-voltage insulating gloves recommended.
* '''Discharge wand (optional)''' – A purpose-built safe discharger for CRTs.

== How to Build a Discharge Tool ==

A simple and safe CRT discharger can be made as follows:

# Attach one end of the alligator clip wire to the metal shaft of a long flat-head screwdriver.
# Attach the other end to a '''ground point on the CRT''' (see below).
# Wrap the shaft in '''electrical tape''' to avoid accidental contact with bare metal.

== Identifying the Ground Point ==

A safe ground point includes:

* The '''metal chassis''' of the CRT tube.
* The '''spring clamp grounding wire''' around the CRT funnel.
* The '''analog board’s metal shield''' or '''logic board ground plane'''.

== Discharge Procedure ==
[[File:CRT Anode Cap.jpg|thumb|CRT Anode Cap]]

=== Step-by-Step ===

# Ensure the system is **unplugged** and left off for 30 minutes.
# Attach your alligator clip to a grounded part of the CRT or chassis.
# Hold the **screwdriver by the insulated handle only**.
# Carefully slide the screwdriver tip '''under the rubber suction cup''' (anode cap) on the CRT.
# You may hear a '''"pop" or crackle sound''' — this is normal.
# Hold contact for at least **10 seconds** to allow the charge to dissipate.
# Remove the anode cap by pinching and lifting it free from the CRT.

=== Repeat Discharge ===
Some CRTs can '''regain charge due to internal capacitance'''. After 10–15 minutes, it's a good idea to '''discharge the anode again''' before handling.

== After Discharge Safety ==

* Always verify the CRT has been discharged before touching or removing the analog board.
* Keep your discharge tool handy during repair in case you need to re-discharge.
* After completing your work, reinstall the anode cap securely and avoid twisting it.

[[Category:Repair Guides]]