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Proper way to GROUND when discharging CRT of compact mac?
- Thread starter gnolivos
- Start date
Sorry I am just getting back to all this. I never heard a zap... I think the CRT was probably all discharged. And to be clear, I grounded to the ground lug following Uniserver's instructions (as that was my reference to begin with). I should have re-read what I wrote and been more clear and said:
Easy first step: "disconnect the Mac from the wall while at full brightness"
And then as a followup: "ground the discharge wire to the ground lug of the computer"
It makes no point to only attach to the ground lug. It attaches to the same chassis. You're just confusing people by being specific. It does not matter. We are not talking a modern set.
Why would you pretend to discharge it? I've never heard of that before.
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Isn't the ground lug the actual 0 V ground reference point? Anything else is just something connected to ground by a wire or the chassis frame, which *should* be at the same potential, but might not be if there's a loose wire or crack/rust in the frame or other unexpected issue. So discharging to the actual ground lug should be safest.
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This is NOT a safe way to discharge the high voltage. You're on the full assumption that the voltage will instantly drain through a number of reasons, including a switched bleeder circuit. If this was the case then just flipping the power switch would achieve the exact same result.
Here's an experiment for all of you. Follow what he described you do, then pop the anode cap off and touch it with your finger. You WILL get electrocuted and it will not be an enjoyable experience.
Just follow my instructions on the last page. This is not a modern TV set. This is a monochrome monitor in a computer from the mid 80's and doesn't have isolated grounding/logic ground or anything of the matter.
You're grasping straws here. Look at how the analog board is attached inside a compact mac. There's multiple points where a strong link is established, some of them screwed together. Apple didn't mandate this. It's required for CSA approval among other certifications. For a failure to occur where the grounds on the analog board and the chassis become isloated, a LOT of places need to be physically not touching eachother.
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I WILL refer you to the source. People read this FIRST, then comment !
"The other one is the older version of the Apple CRT Discharge Tool (Part No. 076-0243). The older version has a copper alligator clip but no hand guard. It has a built-in 100-megohm resistor, which means you will not hear an electrostatic crack when the CRT discharges, even if the monitor has no bleeder resistor. This older tool was designed for the original Macintosh or Macintosh Plus logic board. A resistor was installed to diminish the impact of the electrostatic discharge if a technician accidentally discharged the CRT to the metal chassis instead of to the ground lug. (The Macintosh logic board circuitry is grounded to the chassis.) This older tool is safer for use on the Macintosh or Macintosh Plus CRT."
http://www.biwa.ne.jp/~shamada/fullmac/repairEng.html
"The other one is the older version of the Apple CRT Discharge Tool (Part No. 076-0243). The older version has a copper alligator clip but no hand guard. It has a built-in 100-megohm resistor, which means you will not hear an electrostatic crack when the CRT discharges, even if the monitor has no bleeder resistor. This older tool was designed for the original Macintosh or Macintosh Plus logic board. A resistor was installed to diminish the impact of the electrostatic discharge if a technician accidentally discharged the CRT to the metal chassis instead of to the ground lug. (The Macintosh logic board circuitry is grounded to the chassis.) This older tool is safer for use on the Macintosh or Macintosh Plus CRT."
http://www.biwa.ne.jp/~shamada/fullmac/repairEng.html
I learned to do it this way from someone who has been servicing TV's for almost 25 years and I personally have been discharging anode caps the same way on macs, monitors and TV's for the last five with no ill-effects. Say what you want, I'm done in this thread as well before it gets out of hand.
