Dangers of the CRT ??

[JDW]

Amazing how long this thread is. The question is simple. So is the answer which Dr. Lee provides. Listen to Tom Lee:

viewtopic.php?p=24427#p24427

The "yank the plug" method works, folks. Yes, I've tried it.

 

[srieck]

Well...I got in the and got the board and drives out. Everything was very smooth. Thanks for your advice and information everyone.

If any of you would be kind enough to offer some advice on my sound and RAM issues, please see my "diagnosing my se/30" thread.

 

[H3NRY]

The danger from high voltage is that it might go through your heart, and if it does that at just the critical part of your EKG cycle, it could put you into fibrillation. Sounds scary, huh?

So the old tube TV and guitar amp guys' rule is, if it's hot or you don't KNOW it's safe, keep one hand in your pocket. You may get your right hand zapped if you touch something you shouldn't, but the worst that can happen is a burn on your skin. The zap can't go through your heart. The other danger is you develop a strong instinct to throw things if you get shocked or burnt, and this has resulted in chassis getting launched onto the concrete garage floor when a hand brushes against a hot tube. ;-(

In particular, the dangerous part of a CRT is under the "suction cup", safely insulated. You won't be near that removing the mainboard for recapping. Also, Se30s discharge the high voltage, though I'd still keep one hand in my pocket when disconnecting the suction cup if I were changing the tube or some such.

 

[Hatta]

Since we're on this topic, I thought I'd ask this here. I need to resolder the connector from the analog board to the yoke. My SE/30 has been unplugged for a couple weeks now. Will I need to discharge the CRT?

 

[sirwiggum]

Some useful info here, thank you.

I had initially been a bit put off at taking the classic 2 apart for fear of death. But I shall now investigate the white lines issue.

Also, the mac plus in storage needs some soldering as the video is temperamental. It has been stored for >10 years, so hopefully should have discharged in that time!

 

[protocol7]

Yeah the danger of death fear put me off opening mine up too. Discharging the CRT sounded equally dangerous. However, the Classic II has a bleeder resistor which is designed to remove any charge once the Mac is switched off. As a precaution against the resistor being faulty I left mine unplugged for a week and then opened it up. To remove the logic board I didn't have to go anywhere near the CRT (just disconnect the power, floppy and hd cables) so it was a safe operation.

 

[krye]

I've opened my Macs a dozen times and out of habit I've discharged the CRT every time. Not once have I seen so much as a spark from discharging it. So it must drain after power down.

 

[JDW]

Many "newer" flybacks had a bleeder resistor. So what you are seeing indicates you have one of those flybacks, as evidenced by the fact it drains over time. But the earliest flybacks in the Mac 128k and 512k did not have the bleeder. Hence for some people, discharge is more of an issue. But again, just use the Tom Lee method of full brightness and then a power cord yank. If you practice that you'll never go wrong. That's sometimes important because the bleeder type flybacks don't bleed "instantly." And if you're working with the machine, powering it up and then wanting to work inside, the bleeder wouldn't have had time to discharge the CRT, so you'd need to do that yourself with Tom's method.