JPS6341627Y2 - - Google Patents

Description

[Detailed description of the invention] When the tape recorder of the present invention is in the playback mode, the positioning mode is established by operating the fast forward or rewind operation button, and when a no-signal area between the signals is detected. The present invention relates to a control circuit for a tape recorder having a function of stopping the running of a magnetic tape, and will be described in detail below with reference to the drawings.

The illustrated circuit is one embodiment of the present invention;
2. A playback head that comes into contact with the magnetic tape during playback and positioning operations and plays back signals recorded on the tape; 2. A preamplifier circuit that amplifies the signals reproduced by the playback head 1. 3 is a variable resistor whose one end is connected to the output terminal of the preamplifier circuit 2 and whose other end is grounded via the collector-emitter path of the switching transistor 4; its sliding terminal 5 is connected to the main It is connected to the input terminal of the amplifier circuit 6. 7 is a headphone jack to which the signal from the main amplifier circuit 6 is applied and into which a headphone plug is inserted; between the headphone jack 7 and the output terminal of the main amplifier circuit 6 there is a An attenuation resistor 8 is connected which acts to attenuate the signal level.
9 is a muting control transistor whose collector and emitter are connected to both ends of the attenuating resistor 8; 10 is a mutating control transistor whose collector is connected to the base of the transistor 9 via a resistor 11 in order to control the operation of the mutating control transistor 9; a first transistor 13 whose collector is connected to the base of the transistor 10 via a resistor 10 and whose emitter is connected to the base of the transistor 10 through a resistor 10 in order to control the operation of the first transistor 10; A second transistor is grounded. The bases of the switching transistor 4 and the second transistor 13 are connected to the power supply line 1 through resistors 15, 16 and 17.
Connected to 2. 18 is a control switch that is closed when the fast forward or rewind operation button is operated, and the switching transistor 4 and the second
It is connected to the base circuit of the transistor 13, and has the effect of making the switching transistor 4 and the second transistor 13 non-conductive when it is closed. In such a circuit, the reason why the first transistor 10 is configured of a transistor of a conductivity type opposite to that of the mutating control transistor 9 is that the transistors 9, 1
This is to prevent leakage current when 0 is in a non-conducting state. Reference numeral 19 denotes a no-signal portion detection circuit to which the output signal from the main amplifier circuit 6 is applied and which detects a no-signal portion between the signals recorded on the magnetic tape. It is configured to output a trigger signal. 20 is an inversion circuit such as a flip-flop circuit which performs an inversion operation when a trigger signal is output from the no-signal portion detection circuit 19 and returns to inversion when the control switch 18 is released; 21 drives an electric motor that drives the magnetic tape to run; The motor driving circuit is configured such that when the inversion circuit 20 is inverted by a trigger signal from the no-signal portion detection circuit 19, the output stops the rotation of the motor. 22 is a control transistor whose collector and emitter are connected between the trigger signal path 23 and the ground to control the application of a trigger signal from the no-signal portion detection circuit 19 to the inverting circuit 20; 24 is a control transistor of the control transistor 22; This is a charge/discharge capacitor connected to the base circuit and charged through a diode 25 when the control switch 18 is in an open state, and together with a resistor 26 constitutes a time constant circuit 27 . 28 is a power supply switch that is closed during playback, fast forwarding, and rewinding operations and supplies power to the power supply line 12; 29 is connected between the power supply line 12 and the power supply side terminal of the charging/discharging capacitor 24; This is a quick charging capacitor, and functions to rapidly charge the charging/discharging capacitor 24 when the power supply switch 28 is closed.

The present invention is constructed as described above, and the operation of this circuit will now be explained. When the regeneration operation is performed, the power supply switch 28 is closed and the power supply line 1 is
When power is supplied to 2, the drive mechanism enters the regeneration state. In such a playback operating state, control switch 1
8 is open, switching transistor 4, muting control transistor 9, first transistor 10, second transistor 13
and control transistor 22 are all in a conductive state. The signal reproduced by the reproduction head 1 is applied to a preamplifier circuit 2, amplified, and then introduced to a variable resistor 3. In this state, one end of the variable resistor 3 is grounded by the conduction of the switching transistor 4, so by sliding the sliding terminal 5, the level of the signal input to the main amplifier circuit 6 is brought to zero. It can be varied from up to the maximum.
The signal whose level is adjusted by the variable resistor 3 and input to the main amplifier circuit 6 is further amplified by the main amplifier circuit 6 and then sent to the headphone jack through the collector-emitter path of the muting control transistor 9 which is in a conductive state. It is output to Tsuku 7.
Therefore, the user can listen to the reproduced signal through the headphone connected to the headphone jack 7. In such a reproducing operation state, when a no-signal portion between the signals is detected, a trigger signal is output from the no-signal portion detection circuit 19, but since the control transistor 22 is in a conductive state, the trigger signal is sent to the inverting circuit 20. is not applied to the inverting circuit 20, and the inverting circuit 20 does not perform inverting operation. Therefore, the magnetic tape continues to play without being forced to stop running.

Although the reproducing operation is performed as described above, the positioning operation will be explained next. The positioning operation is performed by operating the fast forward operation button or the rewind operation button while in the playback operation state, and when such operation is performed, the control switch 18 that was in the open state is closed. . When the control switch 18 is closed, the bases of the switching transistor 4, the second transistor 13, and the control transistor 22 are grounded, so that the transistors 4, 1
3 and 22 are reversed to a non-conducting state. When the second transistor 13 is inverted to a non-conducting state, the first transistor 10 whose base is connected to the collector of the transistor 13 is inverted to a non-conducting state, and further a mutating transistor whose base is connected to the collector of the transistor 10 is inverted. Control transistor 9 is reversed to a non-conducting state. In such a positioning operation state, since the switching transistor 4 is in a non-conducting state, the variable resistor 3
does not significantly change the signal level no matter where the sliding terminal 5 is located. The signal reproduced by the reproduction head 1 by high-speed winding or unwinding is applied to the main amplifier circuit 6 through a preamplifier circuit 2 and a variable resistor 3. The signal amplified by the main amplifier circuit 6 is output to the headphone jack 7 through the attenuation resistor 8 since the muting control transistor 9 is in a non-conducting state. Therefore, even if the reproduction output of the reproduction head 1 increases as the tape speed increases, the level of the signal output to the headphone jack 7 can be attenuated to an appropriate level by the attenuation resistor 8. This will not cause any discomfort to the user who is listening to the playback through headphones. In such a state, when the signal from the main amplifier circuit 6 is applied to the no-signal portion detection circuit 19 without being attenuated and a no-signal portion between the signals is detected, the no-signal portion detection circuit 19 outputs a trigger signal. is output. Since the control transistor 22 is in a non-conducting state, the trigger signal from the no-signal portion detection circuit 19 is applied to the inverting circuit 20, causing the inverting circuit 20 to invert. As a result, the motor driving operation by the speed control circuit 21 is stopped, and the magnetic tape stops running.
Then, when the user releases the fast forward operation button or the rewind operation button, the control switch 18 is opened and the reversing circuit 20 is returned to reverse, and the speed control circuit 21 is activated and drives the electric motor to rotate. The recorder changes from the stopped state due to the positioning operation to the playback operation state, and the user can listen to the playback signal by the above-described operation. By performing such an operation, the user can quickly find the location where the desired music or the like is recorded. When the variable resistor 3 is varied in the positioning operation state described above, the signal level changes somewhat, but if the input impedance of the main amplifier circuit 6 is made sufficiently large compared to the impedance of the variable resistor 3, the change can be ignored. It gets smaller.

The reproducing operation and the positioning operation are performed as described above, but the operation at the time of switching will be explained next. If you perform playback from a stopped state, the power supply switch 2
8 is closed and power is supplied to the power line 12. At this time, the charging/discharging capacitor 24 constituting the time constant circuit 27 is instantly charged by the charging current flowing through the rapid charging capacitor 29.
Therefore, as soon as the power supply switch 28 is closed, the control transistor 22 is inverted to a conductive state and blocks the input of a signal to the inverting circuit 20. Therefore, as power is supplied, a noise signal is detected by the no-signal portion detection circuit 19. Even if this occurs, the inversion circuit 20 will not malfunction. Furthermore, when a fast-forward operation or a rewind operation is performed from a stopped state, the power supply switch 28 is closed, but the charge/discharge capacitor 24 is instantly charged as in the above-mentioned playback operation, so the control transistor 22 is turned on to prevent malfunction. This fast-forwarding or rewinding operation which prevents the control switch 18 from being closed so that no charging current is supplied through the diode 25. Therefore, when the electric charge stored in the charging/discharging capacitor 24 is discharged through the resistor 26, the control transistor 22 is reversed to a non-conducting state, but the time constant is changed until the circuits such as the no-signal portion detection circuit 19 stabilize. By setting the time to be longer than the required time, it is possible to reliably prevent malfunctions when the power is turned on. Further, when the fast forward operation or rewind operation button is operated while in the playback operation state, the positioning operation state is established and the control switch 18 is closed as described above, but the control transistor 22 is connected to the charging/discharging cocondenser 24. Since the conductive state is maintained for a predetermined period of time by the discharging current of the charged charges, malfunctions due to noise generated during this switching can be prevented.

In this embodiment, in the positioning operation state,
Since the attenuated signal is output to the headphone jack 7, the presence or absence of the signal can be confirmed by listening operation. Furthermore, if a selection switch for controlling the positioning operation is provided between the output terminal of the main amplifier circuit 6 and the no-signal area detection circuit 19, etc., and the input signal to the no-signal area detection circuit 19 is cut off, the positioning function can be performed. is not activated, and normal queue or review operations are performed.

As explained above, the control circuit of the present invention eliminates the level adjustment effect of the variable resistor that adjusts the level of the signal during positioning operation. Even if the slider of the device is at the minimum position, it can be maintained at a predetermined value or higher, and the no-signal portion detection operation can be performed reliably. In addition, when power is supplied by closing the power supply switch, the control transistor that controls the input operation of the signal from the no-signal detection circuit to the inverting circuit is made conductive immediately. Since malfunctions can be prevented, the practical value of the present invention is extremely high.

[Brief explanation of drawings]

The illustrated circuit is one embodiment of the control circuit of the present invention. Explanation of main figure numbers, 1... Reproduction head, 2... Preamplifier circuit, 3... Variable resistor, 4... Switching transistor, 6... Main amplifier circuit, 7... Headphone jack, 8... ... Attenuation resistor, 9... Muting control transistor, 10... First
Transistor, 12...Power line, 13...Second transistor, 18...Control switch, 19
...No-signal portion detection circuit, 20...Inversion circuit, 21
... Speed control circuit, 22 ... Control transistor, 24 ... Charge/discharge capacitor, 27 ... Time constant circuit, 28 ... Power supply switch, 29 ... Rapid charging capacitor.

Claims (1)

[Scope of utility model registration request] A function that configures the positioning operation state by operating the fast forward or rewind operation button when the tape recorder is in the playback operation state, and also stops the running of the magnetic tape when a no-signal area between signals is detected. A tape recorder having a magnetic tape includes: a playback head that plays back signals recorded on a magnetic tape during playback and positioning operations; a preamplifier circuit that amplifies the signal played by the playback head; a variable resistor whose one end is connected to the output terminal, the other end is grounded via the collector-emitter path of the switching transistor, and whose sliding terminal is connected to the input terminal of the main amplifier circuit; A no-signal portion detection circuit detects a no-signal portion between the signals when the output signal of the amplifier circuit is applied, and an inversion operation occurs when a signal accompanying the no-signal portion detection is output from the no-signal portion detection circuit. an inverting circuit for stopping the running of the magnetic tape; a control transistor connected to control application of a signal from the no-signal portion detection circuit to the inverting circuit; and a control transistor connected to the base circuit of the control transistor. and a time constant circuit including a charge/discharge capacitor that maintains the control transistor in a conductive state for a predetermined period of time when the fast forward or rewind operation button is operated and prevents the signal from the no-signal portion detection circuit from being applied to the inverting circuit. , a control switch which is closed by the operation of the fast forward or rewind operation button, and whose closing causes the switching transistor and the control transistor to become non-conductive, and the time constant circuit when the power supply switch is closed; A control circuit for a tape recorder, characterized in that a quick charging capacitor for rapidly charging the charging/discharging capacitor constituting the tape recorder is connected between a power supply line and the charging/discharging capacitor.