If I'm going to work on a Plus or earlier and need to work with the CRT, I prefer to leave things unplugged for two weeks. In addition to keeping the Mac off, I'll actually unplug it. This should get rid of almost any buildup in there, but to err on the side of caution, discharge the CRT.
I like the cautionary note on discharging, yes this really must be your ultimate goal after popping the case. With all due respect, waiting 2 weeks is unnecessary as a discharge will bleed *all charge* out the CRT, even after it has been plugged in minutes before the discharge procedure. You can do a discharge procedure 2 or 3 times if it makes you feel safer, as a precaution but there is no need to wait two weeks. There really isn't.
Here is a practical example. Let's say I wait those two weeks, maybe because I am truly frightened and believe that allowing this time to go by makes me feel safer. I am not here to argue anyone's fear of something, it's an instinct and natural but in practical terms … let's say I do wait those 2 weeks. My next step would be to remove the case and discharge the CRT. Now I begin work, recapping or whatever, then I reassemble the machine and find that I have not resolved the issue. I will need to switch off the machine, unplug the chord for the outlet, remove the logic board and discharge the CRT. Discharge because I want to avoid any bodily harm and or damage to the computer. I won't wait 2 weeks before proceeding.
Discharging is safe and is in fact a safety step when working on any hardware that has a CRT. If you follow the video closely you will be safe. I can assure you that this is one of the best videos on the topic that I have seen.
I can't remember if it was mentioned in the video, forgive me if it was but remove any jewelry, keep one hand behind your back, don't wear synthetic clothing, do not ground yourself, and when possible, have someone in the room when discharging a CRT.
Here is why:
If something goes wrong, having your hand behind your back will force the charge to travel away from your chest where your heart can really get messed and potentially cause a heart attack. Using cotton versus synthetic clothing will prevent burns, synthetic material is very good at holding a charge and you should never wear synthetics to begin with when working on electronics, it can hold and release enough to zap electronics. Removing jewelry is a precaution incase something does go wrong, the charge would be enough to attract the charge to those metals causing potential burn marks to the body. Having someone in the room is recommended in the event something goes wrong and you are knocked out, that person would be there to call an ambulance.
These sound like extreme precautions but CRTs are not toys.
When at AppleCare, the desktop technician exam was made up of two parts, safety and technical. If a single answer was incorrect in the safety portion of the exam it was enough to fail.
Hope this helps.
Let me tell you a story about my own fears. The first machine that I opened up was an eMac and I had to get near the CRT. I had no idea how to discharge the CRT but I knew that I was dealing with a potentially dangerous repair especially because I was conscious that there was an obvious knowledge gap. I was as scared as can be but I managed to stay clear of any of the high voltage areas. This was years before I passed the apple desktop technician exam. When at AppleCare, I had to discharge a CRT when practicing. The probe was not a screw driver as in Bruce's video, it was actually a very long probe, it was not an official Apple part, why I don't know but it was so long that one would be a few feet away when discharging. I found it to be cumbersome because you actually end up having a hard time getting under the anode cap.
Sorry for the long message but I want anyone coming across this post to be safe and know how to be safe because it helps to feel confident about the procedure and that is always a good thing in my book.
Cheers