JPH0159799B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cathode ray tube display device, in which the cause of the failure of the cathode ray tube screen to be easily identified.

FIG. 1 shows the configuration of the main parts of a conventional color cathode ray tube display device. 1, 2, 3 in the diagram
Output stages for red, green, and blue signals respectively, 4
5 is a color cathode ray tube, 5 is a cathode of the color cathode ray tube 4, 6 is a high voltage generation circuit, and 11, 21, and 31 are output transistors of output stages 1, 2, and 3, respectively.

Normally, a cathode ray tube display device does not emit cross clusters, so the potential of the cathode 5 of the color cathode ray tube 4 is set at a cutoff point so that the color cathode ray tube 4 does not emit light unless a video signal is input. The reason why the screen of the color cathode ray tube 4 does not light up is that, in addition to the case where the video signal is not input as mentioned above, the collectors of the output transistors 11, 21, and 31 of each output stage 1, 2, and 3
A failure such as an open circuit between the emitters may occur, and in either case, the potential of the cathode 5 rises to +B voltage and becomes higher than the cut-off voltage of the color cathode ray tube 4.
The screen no longer lights up.

The second reason is when the high voltage generation circuit 6 malfunctions and high voltage is not applied to the color cathode ray tube 4 and the screen of the color cathode ray tube 4 does not light up, or furthermore, the cathode ray tube itself is defective and the screen does not light up. Conceivable.

There are many possible reasons why the screen of the color cathode ray tube 4 does not shine, and there is a problem in that it is not easy to determine which part is malfunctioning. When this cathode ray tube display device is used as a terminal device such as a computer, it is better to carry out patrol inspections by service personnel, rather than discovering and repairing individual defects. We use a service method that replaces the entire unit. In this situation, it is becoming more important to be able to determine the defective classification of each block than to discover specific defective locations.

Next, a cathode ray tube display device proposed prior to the present invention will be described. An example of this will be explained using FIG. 2. In the figure, the same parts as in FIG. 1 are designated by the same numbers.

In FIG. 2, a switch 7 is added to the circuit of FIG. The connection point A of the voltage dividing resistors 8 and 9 which divides the voltage to a voltage lower than the cut-off voltage of
is connected to.

Now, suppose that the screen of the color cathode ray tube 4 does not light up even though a video signal input is applied, and when the switch 7 is closed, the cathode 5 of the color cathode ray tube 4 is forced to a voltage lower than its cut-off voltage. . Therefore, the color cathode ray tube 4 lights up,
At this time, each transistor 1 of output stages 1, 2, and 3
It can be determined that the color cathode ray tube 4 did not emit light due to failures in the tubes 1, 21, and 31.

Note that if the high voltage generation circuit 6 is out of order, no high voltage is applied to the color cathode ray tube 4 even if the switch 7 is closed, so the screen of the color cathode ray tube 4 will not illuminate. The same applies when the cathode ray tube 4 itself is out of order, and the color cathode ray tube 4 does not emit light.

According to the above configuration, when the screen of the color cathode ray tube does not light up, by closing the switch 7, it is possible to easily determine whether the failure is in the video signal circuit or some other failure, thereby shortening the repair time. Although the effect of making it possible has been produced, Switch 7 is a red flag,
The cathodes 5 of each of the color cathode ray tubes 4 connected to the output stage of the green signal and the blue signal are forced to be set to a voltage lower than the cut-off voltage at the same time until it is possible to easily determine the failure of the output stage of each signal. It didn't belong to me.

The present invention obviates the above-mentioned drawbacks. Examples thereof will be described below with reference to FIGS. 3 to 5. In the figure, the same parts as those in FIG. 1 of the conventional example are designated by the same numbers, and their explanations are omitted.

FIG. 3 is a circuit diagram of a main part of a cathode ray tube display device which is an embodiment of the present invention, and is largely different from the means proposed earlier in FIG.
The point is that the switch circuits are configured independently for each of the red signal, green signal, and blue signal circuits. When the switch 7-1 is closed in the same way as above, the color cathode ray tube 4
The green signal cathode 5 is forcibly set to a voltage lower than its cut-off voltage. If the color cathode ray tube 4 lights up at this time, it can be determined that the transistor 31 or the resistor of the output stage 3 is defective and the color cathode ray tube 4 does not emit light due to a failure.
Similarly, when the switch 7-2 is closed, the green signal cathode 5 of the color cathode ray tube 4 is forced to a voltage lower than its cut-off voltage. If the color cathode ray tube 4 lights up at this time, it can be determined that the transistor 21 or the resistor of the output stage 2 is defective and the color cathode ray tube 4 does not emit light due to a failure. Similarly, if the color cathode ray tube 4 lights up by closing the switch 7-3, it can be determined that the transistor 11 or the resistor in the output stage 1 is defective and the color cathode ray tube 4 does not emit light due to a failure. As in Fig. 2, if the high voltage generation circuit 6 or the cathode ray tube 4 itself is out of order,
Even when the color cathode ray tube 4 is closed, the screen of the color cathode ray tube 4 does not illuminate, for example because high voltage is not applied to the color cathode ray tube 4.

According to this configuration, since the switch can be opened and closed for each color signal, there is an effect that the fault range can be divided into three parts and discriminated. Since it is extremely rare for a failure in each circuit to occur in all output stages at the same time, normally the video signal is detected when a failure in the high voltage generation circuit 6 is detected by opening/closing switches 7-1, 7-2, and 7-3. It is also possible to determine whether an input is being applied or whether the cathode ray tube itself is defective.

FIG. 4 is a circuit diagram of a main part of a cathode ray tube display device according to another embodiment of the present invention, in which a check plug is used in the construction of a switch circuit 7' used to identify and find a failure location. The major difference from the cases in Figures 2 and 3 is that the voltage dividing resistors 8 and 9 are no longer used to supply a voltage lower than the cut-off voltage to the cathode 5, and the bias resistor 10, which is used only during inspection work, is replaced. This is a point that has been established.
One end of the bias resistor 10 is grounded. A check plug 7'b connected to the connecting lead wire 7'a is electrically connected to the other end. The inspection plug 7'b is normally inserted and fixed into the play connector TP0. When used to identify and discover failure locations, they are extracted as appropriate and connected sequentially to test connectors TP1, TP2, and TP3 provided for each color signal. The connection lead wire 7'a may be any wire convenient for temporarily connecting the idle connector TP0 and each test connector P1, TP2, TP3 during inspection work.

Each of the test connectors P1, TP2, and TP3 does not necessarily have to have an insertion/fitting structure with the inspection plug 7'b, but test points may be set using a copper foil pattern or the like to temporarily establish electrical connection. It is. Voltage dividing resistors 8 and 9 that constantly carry current to identify faulty locations that are used very infrequently.
This eliminates the need for a switch in the video output signal circuit, which increases flexibility in circuit design and greatly contributes to cost reduction. Although not shown in the drawings, it goes without saying that if the handle portion of the inspection plug 7'b is made of an insulating material and only the tip portion is made of a conductive material, a safe design can be obtained. Similarly, the connecting lead wire 7'a has a core made of a conductive material and an outer sheath made of an insulating coating. Although both have simple constructions, the effects of the embodiment shown in FIG. 3 are fully demonstrated.

Finally, still another embodiment of the present invention, which can also be used for cut-off voltage adjustment, will be explained using the detailed circuit diagram of the main parts of a color high-definition, three-electron gun, shadow mask type character graphic display device shown in FIG. explain.

The basic configuration is the same as the embodiment shown in FIG.
The difference is that the switch circuit has been changed from a single-pole single-head type to a single-pole double-head slide switch, and an electrolytic capacitor 11 has been added between the connection point A of the voltage dividing resistors 8 and 9 and the ground, and the voltage supplied to the cathode 5 has been changed. The point is that it stabilizes the

Output transistors 51a, 51b, 52a, 52 forming output stages 1', 2', 3' of each color signal
A video signal input from the color signal amplification circuit 12 is applied to each of the bases b, 53a, and 53b. Each emitter of the output transistors 51a-53b is grounded through a resistor, and a blanking signal from blanking circuits 21-23 is applied to each emitter. 51c, 52
53c and 53c are blanking circuit transistors. Furthermore, the output transistors 51a~
Each collector of 53b is connected to the +B2 circuit through a frequency characteristic compensation element and a load resistor, respectively, and switch circuits SW1151, SW1251, and SW1351 are connected to the cathode 5 of the cathode ray tube 4.
is connected to one fixed contact of the The movable contacts of the switch circuit are respectively connected to the cathodes 5 of the corresponding color cathode ray tubes 4. Furthermore, the switch circuits SW1151, SW1251, SW1
The other fixed contact of 351 is the connection point A of voltage dividing resistors 8 and 9, which is commonly connected between the +B2 circuit and ground.
is connected to. The voltage at this connection point A is set to a voltage lower than the cutoff voltage of the color cathode ray tube 4 and which can be used when adjusting the cutoff voltage adjustment circuit 13 of the color cathode ray tube 4. In order to stabilize the potential at connection point A, an electrolytic capacitor 11 is connected between this point and ground. The switch circuit is generally constructed using a slide switch. If the movable contact piece of the slide switch is set to the N side in the drawing, the cathode ray tube display device will be in a normal operating state. On the other hand, by appropriately setting the movable contact piece on the S side in the drawing, the purpose of the present invention, which is to use it for determining a faulty circuit and adjusting the cut-off voltage adjusting circuit 13, can be achieved.

Note that a high voltage of approximately +25 KV is normally supplied to the anode of the color cathode ray tube 4 from a high voltage generating circuit 6. In addition, the focusing electrode is connected to the focusing voltage circuit 14 by approximately +
High voltage of 6KV to +7KV is supplied. and the second
A voltage of about +900 V from a second grid voltage circuit 15 is adjusted by a second grid voltage adjustment circuit 16 and supplied to the grid electrodes individually. 1st
A voltage is supplied to the grid electrodes so that the brightness of the screen of the color cathode ray tube 4 can be varied by adjusting the cut-off voltage adjusting circuit 13 and setting the brightness adjusting volume 17.

Although blanking circuits 21, 22, and 23 are not shown, they perform the operation of applying blanking signals to the emitters of the color signal output transistors by obtaining blanking signals from vertical and horizontal output circuits. .

As is clear from the description of the embodiments described above, this configuration exhibits the effect of not only finding a fault location but also easily adjusting the cut-off voltage.

As is clear from the above embodiments, according to the present invention, by providing a switch that can independently supply a voltage lower than the cut-off voltage to each cathode of a color cathode ray tube, the color cathode ray tube can be If the screen does not light up, you can easily determine whether the cause is a malfunction in the video signal circuit or some other malfunction (high-voltage circuit, cathode ray tube itself), which can shorten repair time. be.

Furthermore, by setting the voltage individually supplied to the cathode to a stable voltage when determining a failure location, it is also possible to rationalize the adjustment process in the cut-off voltage adjustment circuit.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a main part of a conventional cathode ray tube display device, and FIG. 2 is a circuit diagram of a main part of a cathode ray tube display device in an embodiment proposed previously.
FIG. 3 is a circuit diagram of a main part of a cathode ray tube display device according to an embodiment of the present invention, FIG. 4 is a circuit diagram of a main part of a cathode ray tube display device according to another embodiment of the invention, and FIG. FIG. 7 is a detailed circuit diagram of a main part of a cathode ray tube display device in still another embodiment. 1, 1', 2, 2', 3, 3'...output stage, 4...
...Cathode ray tube, 5...Cathode, 6...High pressure generation circuit, 7, 7', 7-1, 7-2, 7-3, SW1
151, SW1251, SW1351... Switch circuit, 8, 9... Voltage dividing resistor, 10... Resistor, 1
1... Electrolytic capacitor, 7'a... Connection lead wire,
7'b...Inspection plug, TP0...Idle connector,
TP1, TP2, TP3...Test connectors.

Claims (1)

[Scope of Claims] 1. A switch circuit configured to supply a video output signal to the cathode of a color cathode ray tube and to be opened and closed independently for each cathode of the color cathode ray tube to which the video output signal is applied. One end of the switch circuit is connected, the other end of the switch circuit is connected to a voltage source that supplies a voltage lower than the cut-off voltage of the color cathode ray tube, and the switch circuit is closed when the screen of the color cathode ray tube is not lit. A cathode ray tube display device characterized by being able to identify locations. 2. A voltage source that supplies a voltage lower than the cut-off voltage of the color cathode ray tube has a first resistor that has one end connected to the voltage supply terminal, and one end that is connected to the other end of this first resistor and the other end that is grounded. a second resistor, and an electrolytic capacitor, one end of which is connected to the connection point between the first and second resistors and the other end of which is grounded, for stabilizing the voltage across the second resistor; 2. A cathode ray tube display device according to claim 1, wherein a voltage lower than said cut-off voltage is supplied from said cut-off voltage.