As a kid I was taught a television still retained energy; even after being unplugged from the power source. I have a 1987 console TV with a nice wood cabinet on a swivel base. I want to remove the innards and make a cabinet for entertainment equipment.
Now, it has NOT been in service for many years and I doubt there is a real shock hazard.
If I did plug the TV back in how long would it take to ensure there was no stored energy? Or am I off base altogether about the energy danger?
Thanks.
-- Oren
"The voices in my head may not be real, but they have some good ideas!"
Two sources of stored charges, big capacitors in the power supply, and the CRT itself which can similarly retain a charge. In most units there are bleeder resistors installed that will drain down the charge within a few minutes. Certainly there is unlikely to be any charge left if the unit has been unplugged overnight. It's mostly an issue for a kid poking around in the TV right after it's been unplugged, or for the service guy working on repairing it and plugging and unplugging it as they work.
The older TV sets had two places to mainly store the energy. The picture tube and some capacitors on the board. If it has been a year or more from the last time it was plugged in I doubt it would have any energy left. If in doubt, you can take a screwdriver and hook a wire to it and then to the chassie and put the screwdriver where the wire comes out of the pucture tube side. Just hold on to the handle of the screwdriver.Thre is often a big rubber plug where the wire goes to the picture tube you must get under to get to the connector.
Not much to worry but I have seen the picture tube retain and even seemingly recharge on its own after years. Just use your head and keep away from the chassis parts and 2nd anode connector atop the tube and you'll be ok.
The unit has been in a friends storage for any number of years and was given to me. I cannot imagine this thing being hot, now, but I don't know ( my guess).
I was a kid, the last time I poked around in a TV. They had tubes back then :-)) When I removed the back cover and looked inside I thought I better ask here.
-- Oren
"The voices in my head may not be real, but they have some good ideas!"
After a few years I doubt it has any stored energy left in it.
Yes, I did mean short the wire comming out the side of the tube to the chassie. The wires at the back of the tube will not have any stored energy in them , but the connection on the side has around 20,000 volts on it when the set is in operation and that is where the voltage is stored.
Not certain on the "anode" or other parts mentioned (G).
I first figured I could snip the wires connecting all the various parts and then remove the fasteners and gut the cabinet. The tube is connected to the chassis (rubber cap/anode?)...
-- Oren
"The voices in my head may not be real, but they have some good ideas!"
Yes that is the high volt lead. Take a jumper from the chassis and a long screwdriver with jumper attached and slide it up under the cap to the center where it clips into the tube just to be sure it's discharged. Then clip the wire. You'll be ok otherwise if you use your head, the rest of the wiring is very unlikely to carry any voltages after this time but you can still take a few sensible precautions as I always would. I've replaced quite a few CRTs in my stint at electronics/tv repair years back.
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 dangerous.
I'm pretty sure the only tube in a 1987 model will be the CRT itself. At any rate, if it's been unplugged that long there is pretty much no chance anything will still have a charge.
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.
Watch out, dielectric absorption can make the voltage stored in the capacitsnce of the picture tubes anode "come back" by itself after you've shoted it out. Doesn't happen often, but not unheard of.
Best to keep your fingers and such away from the picture tube's anode connector at all times.
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 to images.
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 trash.
"Oren" wrote in message news: snipped-for-privacy@4ax.com...
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 washing machine.
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