DE2408656C3 - Circuit for setting the static convergence of the picture tube beams of a color picture tube with three convergence coils - Google Patents

Description

£ 675 2.5 kOhm £ 682 2.5 kOhm £ 676 1 kOhm £ 683 1.2 kOhm £ 677 3.9 kOhm £ 684 270 ohms £ 678 68 ohm £ 685 5.6 kOhm £ 679 5.6 kOhm £ 686 2.5 kOhm £ 680 270 ohm £ 687 220 ohms £ 681 1.2 kOhm + £ = + 25V.

1 sheet of drawings

Claims (2)

Patent claims: 1. Circuit for setting the static convergence of the picture tube rays of a color picture tube with three convergence coils, which are located in bridge circuits adjustable by potentiometers, a first potentiometer circuit for a current change in the same direction in the first and second coil, a second potentiometer circuit for an opposite current change in this first and second coil second coil and a third potentiometer circuit are provided for a current change in the third coil and a simultaneous current change in the first and second coil, which compensates for the mutual influence on the coils, characterized in that the one for the mutual current change in the first and second coil (L002, L003) provided potentiometer circuit is only built up with a simple potentiometer (£ 682). 2. Circuit according to claim 1, characterized in that the first and second coil (L002, L003) are each connected to the ends of the potentiometer (£ 682) via resistors (£ 684, £ 680) and the ends of the potentiometer are in turn connected via resistors (£ 683, £ 681) are connected to one pole (+ £) of the supply voltage and the tap of this potentiometer (£ 682) is connected to the other pole (ground) of the supply voltage. The invention relates to a circuit for adjusting the static convergence of the picture tube beams a color picture tube with three convergence coils in bridge circuits adjustable by potentiometers lie, with a first potentiometer circuit for a current change in the same direction in the first and second coil, a second potentiometer circuit · for an opposite change in current in this first and second coil and a third potentiometer circuit for a current change in the third coil and a die mutual coil influence compensating simultaneous current change in the first and second Coil are provided. A circuit of this type is known (Philips Application Information, No. 264 of December 1 1969), in which the potentiometer circuit provided for the mutual current change in the first and second coil is formed by a double potentiometer. Such double potentiometers with mechanical Couplings of their rotating shafts are on the one hand very expensive and on the other hand also very prone to failure. It is therefore the object of the invention to provide a circuit of this type with regard to the structure of this compensation potentiometer circuit to simplify. This task is based on a circuit of the aforementioned Type solved according to the invention in that the mutual current change in the first and the second coil provided potentiometer circuit only with a simple potentiometer. is built. A particularly simple structure results with a circuit according to the dependent claim. According to the invention, a double potentiometer with its expensive mechanical structure is superfluous Compensation circuit can be used with a simple cheap potentiometer can be realized. A circuit according to the invention is therefore also essential more reliable and less prone to interference, which is very important for modern color television sets. The invention is illustrated below with reference to a schematic drawing of an exemplary embodiment explained in more detail. The figure shows a compensation circuit according to the invention for a color picture tube with a shadow mask beam system. A coil LOOl for the static convergence of the color blue is connected in a bridge circuit, which is formed by resistors £ 676 and £ 677 and from the two parts of a tapping resistor £ 675 . When tuning the resistor /? 675 , the current in the coil LOOl can assume any positive or negative value between 0 and a maximum value, which is determined by the value of a reference potential + R and the values of the resistors £ 676, £ 677 and £ 678 . A coil L002 for the static convergence for the color green is connected in a bridge circuit, on the one hand by resistors £ 683, part of £ 682, £ 684, £ 685 and part of £ 675 and on the other hand from an adjustable divider with resistors £ 687, 686 pounds is formed. The bridge circuit of a red coil L003 is identical and is formed by resistors £ 681, £ 682, £ 680, £ 679, £ 675 and £ 687, £ 686 . When the resistance £ 686 is regulated, the currents in the red coil and the green coil are changed in the same direction; when the resistance £ 682 is regulated, the same currents are changed in opposite directions. In this way a convergence control system is obtained in which the red and green lines can be superimposed in the vertical or horizontal direction. However, it can be seen that when the resistor £ 675 (blue) is regulated, the current in the red and green coils also changes, since the resistor £ 675 is connected to a branch of the bridges that belong to the coils L 002 and L003 . When regulating the resistors £ 682 or £ 686 , the current in the blue coil is also influenced, in view of the fact that the dividers on one side of the bridge of the red and green coils are connected to the tap of £ 675 . In this way the desired compensation for undesired magnetic coupling is obtained between the coils. The values of the circuit elements in a practical embodiment for a 110 ° picture tube are: