On Mon, 24 Sep 2007 19:43:39 -0400, "Ralph Mowery"
Right now the end of the very back of the tube still has components
(coil and green board). I'll clip the glass when I can finally see
the end of the tube's end. Right - I hope....
"If things get any worse, I'll have to ask you to stop helping me."
After years not plugged in the charge should be long gone. On the other
hand there is another danger. It has a large glass envelop. You want to be
careful with it. You don't want to break it with out proper protection for
yourself and anyone else around. They are not real fragile, but they can be
I had an big old console TV several years ago that I needed to discard.
Since our town only took garbage in regulation-sized garbage cans, I had to
break it down into rather small pieces. My biggest worry was the picture
tube, since I had heard that the effect of breaking a large tube could be
measured on the Richter Scale. I dragged the TV out to the back yard,
covered it with heavy quilts like movers use, I dressed in enough layers of
clothing to go exploring Antarctica, I wore an army surplus gas mask (to
protect my face, not because of any gases), a steel helmet, and a pair of
fireman's gloves. If I hadn't been young and impulsive, I probably would
have taken the time to prepare my will. Then I reached over from one side
so I would be shielded by the wood console, took a pair of pliers, and
clipped off the nipple on the back of the picture tube. What happened next
was kind of like the sound you get from opening a beer bottle. A brief
Pffft, and it was over. If it had happened during modern times, it would be
on YouTube now. I used a thick piece of shielded cable and shorted every
dangerous looking connection to ground, but didn't get any sparks or other
signs of residual voltage. Then I removed and smashed the picture tube and
unfastened every screw in sight. It was a bit of work twisting the chassis
into a shape that would fit in the garbage can, and I needed a chainsaw to
deal with the cabinet, but I eventually got the whole thing into garbage
cans over the course of a few weeks. In the end, it was much easier than the
14.7 pounds, unless you're a few feet underwater, but who's counting....
Yes, a CRT implosion can be pretty scary. back around 1952 when I was a
kid working after school at Bud Fiske's Radio & TV shop in San Francisco
I was bringing a big B&W TV console chassis with CRT attached back to
the shop in my car.
I just set it on the back seat and when I slammed on the brakes for
"whatever" it tipped forward, the neck of the CRT hit the back of the
front seat and snapped off, sucking the tube base and gun assembly into
the back of the tube so hard it punched through its face.
What a mess! And what a red face I had when I had to explain what happened.
I've never forgotten the boss's words to me when I got back to the shop.
He said, "Jeff, for a smart kid you do stupid pretty good."
Sorry, I was using the new math (probably remembered 1/2 g).
At high school, a couple teachers tossed a 7" CRT into an empty
classroom and quick closed the door. There was glass everywhere - on top
of lights, on top of window casings.
If they shatter when they break you can have glass shrapnel. I was
taught to give a lot of respect to exposed CRTs.
You never know what tv shows were watched on that tube. If the user
watched all sorts of violence, that tube could blow you to kingdom
come. If they watched all kids cartoons, you will just laugh when it
explodes, and I can not tell you on a public newsgroup, what would
happen if that tv set was used to watch porn videos, and the CRT
blew..... (You'll have to use your own imagination).
Like every one else says, I doubt if there is any energy left but if you
want to play it safe discharge the high voltage on the picture tube before
doing anything. 2 other safety rules taught when I worked for Zenith: when
dealing with high voltage always work with one hand in your pocket and never
work alone. You never know what may happen with a picture tube.
The number would be negative. Doing that will charge it up again, if
the high voltage circuit still works.
As to tube versus transistor, I think the voltages at picture tube are
about the same. The voltage was about 10,000 for B&W sets and went to
25,000 for color sets.
Also big screens, which mean the distance from the electron gun to the
screen has to be greater, need somewhat higher voltage.
Most of it is still there when you turn the set off, but slowly leaks
back, probably through a high ohm resistor put in there for just that
purpose. The big wire on the side of the tube is the anode connector,
and the anode is the the inside of the tv screen.
The cathode is in the neck, partly covered by the deflection coils.
Turn the coils on a B&W and you can make the image turn upside down.
Or you can use a magnet to distort the picture.
On color, it's risky to move anything because it's hard to reposition
later. And a magnet can leave it "gaussed" so that the right color
beams don't go through the right holes. They all have autmatic
degaussing these days, even in 1987, but it takes several or many
times turning the set on for it to work.
They used to put the high voltage parts in a metal cage for safety,
but to make the sets lighter they got rid of all of that!!!
I broke the neck off a few picture tubes. If you just crack t hem it's
fun to hear the noise of the air seeping in, and fun to look at the
beautifully designed electron "gun". One 9inch b&w I broke more off
and used it for a planter, with topsoil etc. It had drainage of
course so I had to be careful not to overwater. The plants did really
well and I wondered if it was the phosphorus inside the screen that
made the difference.
If you break more than the neck off, especially if it still has the
vacuum, I think there is a little, very thin cloud of phosphor that
gets dislodge from the blow, but maybe that was just what I expected
and it didn't happen. Anyhow, I do this sort of thing outside and I
give it time for the cloud to blow away.
And I don't touch the phosphors or I wear gloves.
I especially wanted to see what was in a color picture tube so last
summer I broke one of them open. I already had a gun from another
one, but this time I wanted the shadow mask. I wanted to see how they
made it stay in one place (very important) while being bumped around.
It was in their firmly with a very simple design. The shadow mask has
to have the same curvve as the inside of screen so the distance from
each set of 3 holes is the same. Otherwise, there are color fringes
I do all this after the tube is removed from the set. I want the set
light for throwing out, and I don't want to be working with broken
glass in the set.
Then the whole picture tube goes in a big garbage can. The trash guys
wear leather gloves anyhow, and they don't stick their faces in the
While you can get a good jolt immediately after shutting off the power
on an old tv, espeicially those old tube sets, your fears are over
rated. After you unplug it, let it sit during your dinner and it will
be safe. Or leave it overnight to really feel secure. The biggest
risk spot is the high voltage cable to the CRT (picture tube). Thats
a thick wire with a rubber suction cup (looking) thing that is
attached to the picture tube itself. If you want to work on the tv
soon after unplugging it, just use unsulated plyers to yank that wire
off the CRT, then touch the bare end (under suction cup) to the metal
chassis. The capacitors terminals are under the chassis. Theres no
need to stick your hand down there, but they discharge in minutes
anyhow. Neither of these will kill you (with tv unplugged). It will
just wake you up and make you say the f-word. It's about the same
thing as touching a spark plug wire or electric cattle fence. So,
One word of additional advice.....regarding the suggestion below to: "just
use unsulated plyers to yank that wire off the CRT"...
The connection you are removing from the CRT is the so-called 2nd anode high
voltage connection, and lies beneath a protective insulation 'rubber suction
cup' placed there to prevent accidental contact. The actual connection is a
spring loaded / springy, flexible contact which has been compressed before
insertion into the tube receptacle.
"Yanking it off" adds the very real risk of breaking the glass envelope of
the picture tube. The connector was not designed to be yanked, and moreover,
the glass contact on the tube is also not designed to withstand very much
force / tension. The correct removal technique is to compress the springy
contact, causing its' "hooks" to retract", then gently removing it from the
I hate to nit-pick other excellent advice such as was given below, but the
risk of glass damage and the remote possibility of the CRT imploding are
real issues, and perhaps as dangerous as the issue of a shock hazard. I felt
I had to throw in my 2 cents.
You are correct, I should have been a little more specific on that
point. Actually, since this tv is going to the scrap heap except the
wood cabinet, that wire could just be cut. Just leave the suction cup
part on the CRT. Actually, if cut right at the chassis, take the
plyers and touch that cable to the chassis to be sure the CRT is
drained. The wire should be long enough if cut in this manner.
By the way, is this an old tube set? If it is, tubes are worth some
money to antique rebuilders these days. More than likely most of them
are still good. One bad one can kill a tv. I used to work on tvs
when I was in my teens, and I saved all the tubes. I have boxes of
them. Some day I plan to sell them and I may be sitting on a small
fortune. So, if it is, save the tubes.
On Tue, 25 Sep 2007 01:47:19 -0500, email@example.com wrote:
You got this right in your second post, but afaict, the sentence above
his backwards. Once the wire is off the picture tube, it's not the
wire that holds the voltage, it's the picture tube. It's one big
I' ve been careful with the tv's off, but one time I was measuring
something with the tv on, and my hand didn't slip afaik and I didn
think I did anything wrong, but I guess I got about 2000 volts. I
ended up on the other side of the room. I guess, because my legs
extended, or because of fear. I wasn't hurt but it was scary.
That is, keep it from working. Not damage it.
I plan to sell mine too, but so far, I've asked a couple guys at
hamfests who sell them, and they only want new in box tubes. I have
all mine tested, on a quality tube tester, and have both ratings on
the tubes in wax pencil (and of course, not only can one tube keep a
set from working, but in many cases, the set will work even if one
tube tests bad, so just having a tube of the right name can be
valuable. In fact when tube heaters were in parallel, sometimes a tv
would work fine with a tube completely missing. But don't count on
that. :) I think they were other than the final amp, and the signal
went around the tube socket through other parts.
Anyhow, the two guys I talked to weren't interested. Of course things
can be different in other places, and things can change also.
Back in about 1976, my roommate said he was at the incinerator in
Queens, NY and he saw loads of tubes lying in the sand there. I went
out that night and got about 200, most of them still in the box, and
almost all tested good. Plus I have about 200 I've added, minus the
ones I've used.
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