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Date:      Sun, 28 Sep 1997 19:16:29 +0200
From:      "Julian H. Stacey" <jhs@freebsd.org>
To:        richard@pegasus.com (Richard Foulk)
Cc:        freebsd-hardware@freebsd.org, Mark Mayo <mark@quickweb.com>
Subject:   Re: My monitor's got the Shakes... 
Message-ID:  <199709281716.TAA24022@flip.jhs.no_domain>
In-Reply-To: Your message of "Mon, 22 Sep 1997 00:24:45 -1001." <199709221025.AAA03297@pegasus.com> 

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Reference:
> From:		richard@pegasus.com (Richard Foulk) 
> Date:		Mon, 22 Sep 1997 00:24:45 -1001 
> Message-id:	<199709221025.AAA03297@pegasus.com> 

Hi,

Richard Foulk wrote:
> 
> You might try opening it up and cleaning all the dust away with a soft
> brush.  Dust can make in run hot and encourage arcing.
> 
> Don't get zapped by the high voltage.  Unplug the monitor for a while
> before opening it.

_If_ you really must open the monitor ...

Be aware some capacitors recharge on their own, without needing to be 
connected to a supply ! As I recall that's electrolytics, but it may apply 
to the tube as well, which is also a capacitor in its own right
(think Leyden Jars & look in old Physics books etc :-)

Look to see if the heat has cracked the discharge resistors that are usually
strapped for safety across inbuilt (or even stored-in-a-drawer) high voltage
capacitors. If they're cracked they should be replaced, but you must 
think about what voltage is on them first, even unplugged.

Fiddling with the back of televisions & monitors can kill you if
you get it wrong ... do a lot of thinking ... never use sweaty hands
bear in mind your blood conducts a lot better than your skin ...
so avoid being punctured by solder spikes ...
never touch anything dubious with the inside of your hand,
'cos of tendency to reflex grip it, if you must touch, use outside of hand,
dont even think of touching the HT section, & the big thick cable out of
the side of the monitor.
DC will electrocute you better than AC from the outlet,
High voltages obviously more so too :-)

... best way to kill yourself ?  .. current up one arm,
throught the heart ... down the other arm ... try to avoid that scenario:
Think rubber mats & shoes, have wooden sticks to prod with, not screwdrivers,
keep one hand behind your back (not leaning on the table)

If in doubt ... don't ! don't even think of it !

PS I spent a minute or 2 in the High Voltage lab at Leeds University years ago
scared in the extreme ... in pitch dark, with about half a MegV or something
ridiculous in the room, powered up .. some idiot's idea of a prank,
I've also worked on the back of live colour TVs ... neither experiences
are ones to relish ...
I love 5V TTL & the feeling I'll blow the CPU, not me :-)

"Take care" seems the best form of parting salutation ;-)

Julian
--
Julian H. Stacey       jhs@freebsd.org         http://www.freebsd.org/~jhs/



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