Upon the date 04:35 PM 2/22/99 -0500, R. Stricklin (kjaeros) said something
like:
>On Mon, 22 Feb 1999, William Donzelli wrote:
>
>> Post 1960 CRTs are actually quite tough and will sustain a great deal of
>> physical abuse. When they break, the neck shatters first and lets all the
>> air in. The days of the nasty implosions due to no safety glass are gone.
>
>Hm. You're certain? I have this disembodied memory of seeing a box in my
>parents' shed in the early '80s, with an implosion hazard warning
>emblazoned on. I'm fairly sure it was the box for their old TRS-80 Model
>III, but it is possible it belonged to their Zenith TV they'd just bought.
>
>Maybe it was just a bozo-warning.
Yes it probably was a bozo-warning (I like that expression. Gotta remember
it. :)
I've handled CRTs since I was 11 or 12 (33-34 yrs ago). There were those
that were dead and had to be disposed of from a set I was repairing. When
throwing them into the town dump (that's back in the days before controlled
landfills and waste management laws, etc.) I was able to observe that they
would take quite a whack on the side of the large part of the envelope
before they broke. BUT, when they did break, the implosion caused glass
pieces to fly several meters distant. On the other hand, when just the neck
got broke, there was usually a definite, brief "chufff" sound when the air
rushed into the envelope and no other drastic action.
Here's a story to illustrate effects of an implosion: Back when I was
getting more and more into TV repairs during my 17th summer, there was a
dead 19" 110 degree deflection CRT that I had to get rid of. It was setting
on the ledge of the basement foundation wall. Dad was helping me sort out
and haul some junk to the dump. That CRT had to go in that load. Dad
figured he could simply break up that tube to save space on the load as we
were using the rather small family car to haul it (a '65 Corvair). Well, as
he'd never himself broke a CRT nor even seen what happens during an
implosion he was unaware of the "proper" way to bust one up. He held a
corrugated box under the edge of the wall where the tube was sitting,
grabbed a hammer and gave the side of the envelope a firm whack. Naturally,
just as I started to say "Don't hit it there!!", the deed was done. At
least knew enough to hold his eyes closed.
A few minutes later, after we both picked the broken glass out of our hair,
we observed that the largest piece of that tube was not even the size of a
fist. Mom came running downstairs and asked what in the world was going on
with that loud 'bang' and glass shattering sounds. Took a while to get the
place cleaned up. And you can bet that my mother was there watching us to
make darn sure we _did_ clean it up well.
Just understand the neck of a CRT is not so fragile to just break while
twisting a yoke after its clamp is loosened.
Use common sense while working around a CRT. Don't work in a tight area
where you could turn around and accidentally bump the neck with your elbow.
Have plenty room around the monitor while on the table or workbench. Don't
drop tools onto the CRT (happened to me once --and _only_ once!). Careful
of getting zapped by any unprotected parts of the yoke while under power
and rotating it (you could jerk around and bump the neck). There usually is
a part of the plastic yoke body with which you gould grasp while rotating.
The high voltage lead going to the ultor connection on the side of the
envelope handles about 15 to 18 thousand volts for a monochrome monitor.
Don't get close to the lead or especially the ultor connection.
Following these hints should help anybody here get through a simple yoke
adjustment like this.
Christian Fandt, Electronic/Electrical Historian
Jamestown, NY USA cfandt_at_netsync.net
Member of Antique Wireless Association
URL:
http://www.ggw.org/awa
Received on Mon Feb 22 1999 - 17:10:58 GMT