where does a cathode ray tube hold a painful charge (even when it is turned off)?

Question

i have hard that it can hold a strong charge for as long as a year, where are these charges kept inside of the crt
is it in the focusing coils

Answer 1

No, it's not the deflection and/or focusing coils. Being an inductive load, coils lose their energy when the current stops flowing and the magnetic field collapses.

CRT's, including television picture tubes, store a substantial charge of static electricity because they act as high voltage capacitors. The first capacitors were called "Leyden Jars" and were similar to a CRT in that they both are a glass vessel, coated inside and out with a metallic (conductive) coating. The two coatings can be visualized as the two plates of a capacitor with the glass vessel acting as the dielectric. For an oscilloscope's CRT or a television's picture tube, the outside coating is grounded. On the side of the tube you'll see the anode lead-wire with a big rubber cap. The anode wire connects to the inside coating of the tube. NEVER touch anything associated with a CRT's anode because it can literally kill you -- even if the set's been off for a year or more. There are, or course, techniques routinely used to safely discharge a picture tube. Do not attempt to do this unless you being directly supervised by an experienced technician who is very familiar with the procedure. A large color picture tube is as lethal as a loaded shotgun if you don't know what you're doing!

Answer 2

Any CRT requires a high potential difference between the cathode where the beam starts and the face where the phosphors are. This causes the a high striking energy and if too high, a lot of x-rays as well. For television and video uses only, this dc potential is derived from the horizontal sync pulses which are such high frequency that the capacitance needed to smooth this to dc is fairly low. The voltages are so high that using an outboard "capacitor" component is not practical, so the required capacity is built into the CRT structure. If this voltage is not drained off by an external leakage current, it can stay charged up for a long time. Technicians that have to work with CRT circuits will "short" the HV anode on the side of the tube to ground for safety before handling the tube using a HV probe and meter.

Answer 3

In order to attract electrons from the electron gun in the neck of the CRT, there must be a very high positive voltage present at the front end of the CRT. In color picture tubes this can be in excess of 20,000 volts.

Inside the CRT near the front face is a coating of conductive material to help attract the electrons. The coating is connected to a single electrical connection then to a sealed electrode through the thick glass. This is called the anode. The high positive voltage is applied to the anode.

When electrons travel from the electron gun to the face of the CRT to light up the phosphors, there is also a metal mask that is connected to the coating on the inside of the CRT. The electrons make their way back to the anode connection, BUT when the CRT is turned off there is still high voltage present for a short time, that leaves a positive charge inside the CRT.

The coating is no where near the electron gun, and the glass of the CRT is thick -- this makes an excellent capacitor with very little leakage, so that charge (and the high voltage) can remain for a long time.

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Answer 4

no, the focusing coils do carry a potent charge, but are dead after power down.
The Picture tubehas a hole on the side, ware the wire with the rubbershield connects , delevering a 120.00 volt charge lights the screen up. that is the most dangerious part of the picture tube, other than the massive vacume inside of the tube.

A picture can be discharged totally, and be recharged back to lethal voltage, by simpling rubbing a flannel shirt across the glass face plate. those items are for those who know how to safely deal with them.

Answer 5

Due to the collection of the electrons stored by the dark substance called aqua dag? on the outside of the tube.

Answer 6

the place I stay a good number of issues would properly be recycled at our community recycling center run via the city. i'm optimistic there is one on your section. in the event that they do no longer take them i'm optimistic they are going to be attentive to who will.