JPS634289Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an operation circuit for a tape recorder that can set the tape drive mechanism to a predetermined operating position by trigger operations such as playback, fast forward, and rewind.

That is, in recent years, it has become possible to set the tape drive mechanism to a predetermined operating position by trigger operations such as playback, fast forward, and rewind, by effectively utilizing the rotational driving force of the motor without using a plunger or the like. Many soft-touch operation tape recorders have been commercialized. For example, the first
As shown in the figure, a motor 2 and a preamplifier circuit 3 are connected via a trigger switch 1 that is turned ON when a trigger is operated using each operation button such as playback, fast forward, rewind, etc.
After supplying power to the bias circuit 4, etc., and setting the tape drive mechanism (not shown) to a predetermined operating position by the rotational driving force of the motor 2, the trigger switch 1 is turned OFF again. After that, power is supplied to the motor 2, preamplifier circuit 3, bias circuit 4, etc. via the main switch 5, which is closed until the tape drive mechanism is set to a predetermined operating position. . In addition, 6 is the radio/tape selector switch, which is turned on when using the radio.
In this state, power is supplied to the preamplifier circuit 3, bias circuit 4, etc. except for the motor 2. Also,
Reference numeral 7 denotes an input terminal to which an audio signal is input from a magnetic head or a tuner unit, etc. The audio signal input to the input terminal 7 is amplified by a preamplifier circuit 3 and then sent to a speaker as a load through a signal line 8. It is applied to the connected output amplifier circuit, etc. As a mechanism for setting the tape drive mechanism section to a predetermined operating position by the rotational driving force of the motor 2, a toothless gear 9 as shown in FIG. 2 is generally used, and the toothless gear 9 is in a stopped state. Although the toothless portion 9a faces the drive gear 10 and is in a non-meshing state with the drive gear 10, it is rotated slightly by a separate trigger means (in this case, counterclockwise) during each trigger operation such as playback, fast forward, and rewind. direction) and the drive gear 1
0, and after one rotation, the toothless part 9a is engaged again.
corresponds to a non-meshing state. That is, the tape drive mechanism section is configured to be set at a predetermined operating position by receiving the rotational driving force during one rotation of the partially toothed gear 9. It is assumed that the drive gear 10 is formed coaxially with a flywheel (not shown) to which rotational driving force is transmitted from the motor 2, for example. Then, the trigger switch 1
ON/OFF control is performed by a timing cam 9b formed on the top surface of the partially toothed gear 9.
In the stopped state as shown in the figure, the partially toothed gear 9 is connected to the drive gear 1.
0 and the trigger switch 1 is in a non-meshing state.
The actuating piece 1a is switched to the contact OFF side by contact with the timing cam 9b, and in such a state, when triggering operations such as playback, fast forwarding, rewinding, etc., the partially toothed gear 9 is activated by a separate trigger means. When the timing cam 9b is slightly rotated, the timing cam 9b is removed from the actuating piece 1a, and the actuating piece 1a is switched to the contact ON side.

Therefore, the trigger switch 1 is turned ON at each trigger operation, and after one rotation of the partially toothed gear 9 (that is, after the tape drive mechanism is set to a predetermined operating position), the timing cam 9b is turned to the operating piece again. 1
When it comes into contact with a, it becomes OFF state.

However, in this type of tape recorder, the tape drive mechanism is set at a predetermined operating position by the rotational driving force of the partially toothed gear while it rotates once (that is, while the trigger switch is in the ON state). Because of this configuration, tape running becomes unstable during that time. That is, the time chart is shown in Fig. 3, where a indicates the switching operation of the tape drive mechanism, b indicates the ON/OFF operation of the main switch, and c indicates the ON/OFF operation of the trigger switch. During operation, an unstable tape running period T occurs in the tape drive mechanism section. If the amplifier circuit, bias oscillation circuit, etc. are in operation during such a period, for example, during playback operations, the playback signal from the magnetic head is amplified by the amplifier circuit and then emitted from the speaker via the signal line, producing unpleasant rising noise. There was a risk that the bias signal would be recorded as an audible frequency during a recording operation and would be reproduced as an unpleasant rising sound during playback. Similarly, there was a risk that an unpleasant falling sound would be produced during the stop operation.

The present invention has been developed in view of this point, and the output signal from the amplifier circuit is not applied to the speaker etc. through the signal line during the unstable tape running period until the tape drive mechanism is completely set to the operating position. It is an object of the present invention to provide an operating circuit for a tape recorder which is capable of making the bias oscillation circuit inoperable.

An embodiment of the present invention will be described below with reference to the drawings. Note that parts that are the same as those in the prior art will be given the same drawing numbers and their explanations will be omitted.

That is, 11 in the figure is a switching circuit;
2 is a first switching transistor whose collector is connected to the OFF side of the trigger switch 1 via a resistor 13 and whose emitter is grounded; and 14 whose emitter is connected to the movable piece 6a of the radio tape changeover switch 6; and a second transistor connected to the base of the first switching transistor 12 via dividing resistors 15 and 16.
This switching transistor has its collector grounded through a resistor 17 and its base connected to the contact OFF side of the trigger switch 1. 18 is a muting circuit, and a muting transistor 19 whose collector and emitter are connected between the signal line 8 and the ground.
and a time constant circuit 22 consisting of a resistor 20 and a capacitor 21, and the base of the mutating transistor 19 is connected to the collector of the second switching transistor 14 via resistors 20 and 23. Reference numeral 24 denotes a driving transistor whose collector and emitter are connected between the bias oscillation circuit 4 and the power supply, and whose base is connected to the collector of the second switching transistor 14. Note that 25 is an output amplifier circuit to which a speaker or the like is connected as a load.

Therefore, for example, when a playback trigger operation is performed, the trigger switch 1 is turned on,
Power is supplied to the motor 2, preamplifier circuit 3, etc. via the trigger switch 1, and the tape drive mechanism begins to be switched to a predetermined operating position. Therefore, the first switching transistor 12 becomes conductive through the resistor 15, and the second switching transistor 14 also becomes conductive through the resistor 13 due to the conduction of the first switching transistor 12. Therefore, the muting transistor 19 becomes conductive and the driving transistor 24 becomes non-conductive, thereby bypassing the audio signal on the signal line 8 and setting the bias oscillation circuit 4 to a non-operating state.

That is, during the unstable tape running period until the tape drive mechanism is completely set to the playback position, the audio signal input to the input terminal 7 is amplified by the preamplifier circuit 3 and then output through the signal line 8. Amplifier circuit 2
5, and there is no risk of the sound being emitted from the speaker as an unpleasant rising sound. Similarly, since the bias oscillation circuit 4 is set to a non-operating state during a recording operation, there is no risk that the bias signal will be recorded as an audible frequency and emitted from the speaker as an unpleasant rising sound during playback.

After the tape drive mechanism is set to a predetermined playback position, the trigger switch 1 is turned on again.
When the switch is turned off, a cut-off voltage is applied to the base of the second switching transistor 14 through the trigger switch 1, and the second switching transistor 14 is inverted to a non-conducting state. Therefore, the mutating transistor 1
The driving transistor 9 is inverted to a non-conducting state, the driving transistor 24 is inverted to a conducting state, the audio signal on the signal line 8 is applied to the output amplifying circuit 25, and the bias oscillation circuit 4 is in an operating state.

Next, when the stop trigger operation is performed in such a state, the trigger switch 1 is turned on, so the second switching transistor 14 becomes conductive again, and the signal Muting is applied to the line 8, and the bias oscillation circuit 4 is set to a non-operating state.

As described above, according to the circuit of the present invention, the trigger switch that is turned ON when each trigger operation such as playback, fast forward, rewind, and stop is used, until the tape drive mechanism is set to a predetermined operating position. During the period of unstable tape running, the audio signal on the signal line is bypassed and the bias oscillation circuit is made inactive. There is no risk that the audio signal will be applied to the speaker etc. through the signal line and emitted from the speaker as an unpleasant rising or falling sound, and there is no risk that the bias signal will be recorded as an audible frequency during the recording operation. The effect is of extremely high practical value.

[Brief explanation of the drawing]

Fig. 1 is a conventional circuit diagram, Fig. 2 is a schematic configuration diagram of a mechanism for setting the tape drive mechanism to a predetermined operating position, Fig. 3 is a time chart thereof, and Fig. 4 is an embodiment of the present invention. FIG. 1...Trigger switch, 2...Motor, 4
...Bias oscillation circuit, 8...Signal line, 11 ...
...switching circuit, 18 ...mutating circuit.

Claims (1)

[Scope of utility model registration request] During each trigger operation such as playback, fast forwarding, rewinding, etc., the trigger switch is switched to the ON contact side to supply power to the motor, etc., and the tape drive mechanism is set to a predetermined operating position by the rotational force of the motor. The latter is a tape recorder that switches the trigger switch to the OFF contact side again, and power is supplied through the ON contact side and OFF contact side of the trigger switch, and the first control is performed while power is being supplied through the ON contact side. Output the signal and
a switching circuit that outputs a second control signal while power is being supplied through the OFF contact side; and a muting circuit that is controlled in operation by the first or second control signal from the switching circuit and bypasses the audio signal on the signal line in the operating state. A tape recorder comprising a circuit, wherein the switching circuit sets the muting circuit to an operating state by a first control signal thereof, and sets the muting circuit to a non-operating state by a second control signal. operation circuit.