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Re: PowerMac won't turn on after sitting in a cold bedroom

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nospam wrote:
>
> a flyback transformer, on the other hand, can hold a charge for a
> while. those need special care.

It isn't the flyback, it's the CRT connected to it. That can hold lethal
voltages for years.

The standard procedure was to use a screwdriver wired to ground (the metal
parts of the TV chassis) to discharge it. Lots of spark and a loud bang.

No harm done except for some wet pants if you did not touch the anything
except the insulated handle of the screwdriver. 

The original Macintosh had a problem were there was an IC in the circuit that
the spark would destroy. The only safe way was to discharge it relatively
slowly with a probe containing a 1 mega ohm resistor in it.

Apple eventually wised up, and the SE used a flyback with a bleeder resistor
in it, so that after about 10 minutes, the CRT was completely discharged
and safe. It may been sooner, buy I am overly cautious.

The simple way to tell on compact Macs, was if the power supply was enclosed, 
the flyback had a bleeder. If it was discrete components, it did not.

Geoff.




-- 
Geoffrey S. Mendelson,  N3OWJ/4X1GM/KBUH7245/KBUW5379

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Thread

PowerMac won't turn on after sitting in a cold bedroom super70s <super70s@super70s.invalid> - 2014-03-07 21:36 -0600
  Re: PowerMac won't turn on after sitting in a cold bedroom Savageduck <savageduck1@{REMOVESPAM}me.com> - 2014-03-07 21:37 -0800
    Re: PowerMac won't turn on after sitting in a cold bedroom John Albert <j.albert@snet.net> - 2014-03-08 16:17 -0500
      Re: PowerMac won't turn on after sitting in a cold bedroom Your Name <YourName@YourISP.com> - 2014-03-09 12:12 +1300
        Re: PowerMac won't turn on after sitting in a cold bedroom super70s <super70s@super70s.invalid> - 2014-03-09 17:17 -0500
          Re: PowerMac won't turn on after sitting in a cold bedroom Jolly Roger <jollyroger@pobox.com> - 2014-03-09 23:06 +0000
            Re: PowerMac won't turn on after sitting in a cold bedroom super70s <super70s@super70s.invalid> - 2014-03-09 18:26 -0500
              Re: PowerMac won't turn on after sitting in a cold bedroom super70s <super70s@super70s.invalid> - 2014-03-09 18:53 -0500
                Re: PowerMac won't turn on after sitting in a cold bedroom Jolly Roger <jollyroger@pobox.com> - 2014-03-10 00:48 +0000
                Re: PowerMac won't turn on after sitting in a cold bedroom super70s <super70s@super70s.invalid> - 2014-03-09 20:58 -0500
                Re: PowerMac won't turn on after sitting in a cold bedroom Your Name <YourName@YourISP.com> - 2014-03-10 16:49 +1300
                Re: PowerMac won't turn on after sitting in a cold bedroom Jolly Roger <jollyroger@pobox.com> - 2014-03-10 15:30 +0000
                Re: PowerMac won't turn on after sitting in a cold bedroom Barry OGrady <atheist@hotmail.com.au> - 2014-03-22 10:54 +1100
                Re: PowerMac won't turn on after sitting in a cold bedroom Jolly Roger <jollyroger@pobox.com> - 2014-03-22 01:18 +0000
                Re: PowerMac won't turn on after sitting in a cold bedroom Alan Browne <alan.browne@FreelunchVideotron.ca> - 2014-03-10 17:05 -0400
                Re: PowerMac won't turn on after sitting in a cold bedroom nospam <nospam@nospam.invalid> - 2014-03-10 17:41 -0400
                Re: PowerMac won't turn on after sitting in a cold bedroom "Geoffrey S. Mendelson" <gsm@mendelson.com> - 2014-03-11 01:29 +0000
                Re: PowerMac won't turn on after sitting in a cold bedroom nospam <nospam@nospam.invalid> - 2014-03-10 21:48 -0400
                Re: PowerMac won't turn on after sitting in a cold bedroom "Geoffrey S. Mendelson" <gsm@mendelson.com> - 2014-03-11 05:49 +0000
                Re: PowerMac won't turn on after sitting in a cold bedroom nospam <nospam@nospam.invalid> - 2014-03-11 02:12 -0400
                Re: PowerMac won't turn on after sitting in a cold bedroom Jolly Roger <jollyroger@pobox.com> - 2014-03-10 15:28 +0000

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