JPS634244Y2 - - Google Patents

Description

[Detailed description of the invention] This invention uses an audio erasing head and a full-width erasing head in an erasing circuit for a video tape recorder, which is equipped with an audio erasing head for erasing audio tracks and a full-width erasing head for erasing all tracks. The present invention relates to an erasing circuit for a video tape recorder which is operated by an oscillation signal from a separate oscillation circuit, reduces power consumption, and has an inexpensive circuit configuration.

As shown in FIG. 1, the erasing circuit of a conventional video tape recorder has a first power supply terminal Ia to which power is applied when recording a signal only on the audio track of the videotape, an audio track of the videotape, A second power supply terminal Ib is provided to which power is applied when recording signals on the image track, control track, ie, all tracks, and the oscillation circuit 1 oscillates with power from both power supply terminals Ia and Ib. Furthermore, current flows through the relay coil lr of the relay device RY due to the power from the first power terminal Ia, and the connection of the common contact c of the relay device RY is switched from the off contact b to the on contact a.

When recording the signals of all tracks, the common contact c of the relay device RY is connected to the off contact b, and the oscillation signal of the oscillation circuit 1 is transmitted to the audio erasing head Ha, the common contact c of the relay device RY, and the off contact b. , is output to the full-width erasing head Hb, both erasing heads Ha and Hb operate, the video tape TP runs in the direction shown by the arrow in the figure, and all tracks on the video tape TP are erased.

Next, when recording a signal only on the audio track, as described above, current flows through the relay coil lr of the relay device RY, the connection of the common contact c is switched from the off contact b to the on contact a, and the oscillation circuit 1
The oscillation signal is sent to the audio cancellation head Ha and the relay device.
The common contact c and the on contact a of RY are output to an equivalent coil le having an impedance component equivalent to that of the full width erasing head Hb, and only the audio track of the video tape is erased.

However, in the above case, both erasing heads Ha and Hb continue to operate while signals are being recorded on all tracks, resulting in a disadvantage of high power consumption. Furthermore, in order to erase only the audio track and perform so-called after-recording, an expensive relay device RY must be provided, which has the disadvantage of being expensive.

This invention has been made with the above-mentioned points in mind, and next, this invention will be explained in detail with reference to the drawings from FIG. 2 onwards showing an embodiment thereof.

First, FIGS. 2 and 3 showing one embodiment will be explained.

As shown in FIG. 2, when recording a signal only on the audio track of the videotape TP, power from the first power supply terminal Ia is applied to the first oscillation circuit 2a, and the first oscillation circuit 2a is driven. At the same time, the oscillation signal from the first oscillation circuit 2a is transmitted to the audio cancellation head.
The audio track of the videotape TP, which runs only in the direction of the arrow in the figure, is erased.

That is, as shown in Figure 3, the audio track
A videotape TP consisting of TRa, an image track TRb, and a control track TRc runs in the direction of the arrow, and the signal of the audio track TRa is erased by the audio erasing head Ha, and the recording/reproducing head installed adjacent to the audio erasing head Ha. A signal is recorded on the erased audio track TRa by Hc.
In addition, in the opposite direction to the running direction of the videotape TP,
A full width erasing head Hb is provided at a distance L from the audio erasing head Hb, and a video rotating head (not shown) is provided between the distance L.

Next, all tracks TRa of videotape TP,
When recording signals on TRb and TRc, as shown in Figure 2, the power from the second power supply terminal Ib is
The signal is supplied to the oscillation circuit 2b, and the second oscillation circuit 2b is driven. At the same time, the oscillation signal from the second oscillation circuit 2b flows to the full-width erase head Hb, and the full-width erase head Hb operates. In addition, power from the second power supply terminal Ib is input to the first oscillation circuit 2a via the emitter and collector of the first PNP transistor Q1, which is a switching element, and the oscillation signal of the first oscillation circuit 2a generates audio. Erase head Ha operates. In addition, the full width erase head Hb has an erase rate of 65 dB.
With the above, erasure can be performed satisfactorily.

Furthermore, the first time constant capacitor C1 starts to be charged by the power from the second power supply terminal Ib via the first time constant resistor R1. Note that a time constant circuit is configured by the first resistor R1 and the first capacitor C1. And the first capacitor C
1 output potential, that is, the charging potential is the first resistor R1.
and the first capacitor C1, and when the videotape TP travels the distance L shown in FIG. The second transistor Q2 is turned on, and the collector potential of the second transistor Q2, to which the power supply voltage has been applied, is lowered by the power supply voltage through the third resistor R3, and the fourth resistor R
The third NPN type transistor Q3 is turned off by the collector potential of the second transistor Q2 via the transistor Q4. Note that R5 and R6 are the fifth and sixth resistors,
A fifth resistor R5 is provided for the base bias of the second transistor Q2, and a sixth resistor R6 is provided for the base bias of the third transistor Q3.

Then, by turning off the third transistor Q3,
A seventh resistor R7 is connected to the base of the first transistor Q1.
is applied, the first transistor Q1 is turned off, and the power supplied to the first oscillation circuit 2a is cut off by turning off the first transistor Q1, and the oscillation signal from the first oscillation circuit 2a is and the operation of the audio erasing head Ha stops. Note that R8 connects the base of the first transistor Q1 and the third
The eighth bias resistor A1 provided between the transistor Q3 and the collector is a control circuit having a circuit configuration shown by a broken line.

Therefore, according to the embodiment, when recording signals on all tracks TRa, TRb, and TRc of the videotape TP, the audio erasing head Ha is operated for a predetermined period of time.
In other words, it is operated only while the videotape TP travels the distance L shown in Fig. 3, and then the full-width erasing head is operated.
It is possible to operate only Hb, and it is possible to prevent erasing again by the audio erasing head Ha after erasing with the full-width erasing head Hb, preventing so-called double erasing, and greatly reducing power consumption. According to experiments, the audio erasure head Ha
Compared to the erase circuit of a conventional video tape recorder, which continues to operate both the erase head and the full width erase head Hb,
Power consumption can be reduced by 30%, making it suitable for portable video tape recorders where low power consumption is desired.

In addition, for so-called after-recording, which erases only the audio track TRa, there is no need to provide an expensive relay device RY like in the past.
An inexpensive circuit configuration can be achieved.

Next, FIGS. 4 to 6 show other embodiments.
The diagram will be explained.

In Figures 4 to 6, Figures 2 and 3
The same symbols as in the figure indicate the same thing, and the difference from FIGS. 2 and 3 is that a reproduction control head Hd for reproducing the signal recorded on the control track TRc is provided coaxially with the audio erasing head Ha.
As shown in FIG. 5, the audio erasing head Ha and the playback control head Hd are arranged integrally by a so-called double gap system, and the control circuit A2
A control signal discrimination circuit, that is, a detection circuit 3, outputs a detection signal when a control signal from the playback control head HD is input.
Another point is that the power supply circuit 4 supplies power from the second power supply terminal Ib to the first oscillation circuit 2a only while the detection signal of the detection circuit 3 is being outputted.

Then, when recording a signal only on the audio track TRa, the first oscillation circuit 2a is driven by the power from the first power supply terminal Ia, and only the audio erasing head Ha is operated, and all tracks are recorded.
When recording signals to TRa, TRb, and TRc,
The power supply power from the second power supply terminal Ib is supplied to the second oscillation circuit 2.
b, the second oscillation circuit 2b is driven, and the full-width erase head Hb is operated by the oscillation signal of the second oscillation circuit 2b. Also, videotape
When the TP travels in the direction of the arrow in Fig. 6, the control signal recorded on the control track TRc between the full-width erasing head Hb and the audio erasing head Ha, that is, the distance L, is transmitted to the playback control head Hd.
The reproduced control signal is input to the detection circuit 3, and while the video tape TP travels a distance L, a detection signal is output from the detection circuit 3 to the power supply circuit 4, and from the second power supply terminal Ib. is supplied to the first oscillation circuit 2a via the power supply circuit 4, and the first oscillation circuit 2a is driven for a distance L, and the oscillation signal of the first oscillation circuit 2a causes the audio cancellation head Ha to be activated. Operate.

Furthermore, when the videotape TP travels a distance L, the control track TRc erased by the full-width erase head Hb is played back by the playback control head Hd, and
Control signals are no longer output from the HD.
The detection signal from the detection circuit 3 is also no longer output,
The operation of the power supply circuit 4 stops, and the second power supply terminal Ib
Then, the power supplied to the first oscillation circuit 2a is cut off, and the operation of the audio erasing head Ha is stopped.

Therefore, according to the embodiment, when recording signals on all the tracks TRa, TRb, TRc of the videotape TP, the audio erasing head Ha and the full width erasing head Hb are activated only while the videotape TP travels the distance L. After that, only the full-width erase head Hb is operated, thereby preventing so-called double erasing and greatly reducing power consumption.

In addition, since the operation of the audio erasing head Ha is controlled by the control signal from the playback control head Hd, for example, while the video tape TP has traveled a distance L, the running of the video tape TP may be temporarily stopped, or when the video tape TP is Even if the running speed of the
The audio erasing head Ha can be operated only during the distance L from Ha to the full-width erasing head Hb, after which the erasing head Ha can be stopped.

Furthermore, so-called after-recording, which erases only the audio track TRa, can be performed without providing the conventional expensive relay device RY.

Next, FIG. 7 showing still another embodiment will be described.

In FIG. 7, the same symbols as in FIG. 2 indicate the same things, and the difference from FIG. is connected to the first power supply terminal Ia, the other input terminal of the OR gate G is connected to the second power supply terminal Ib, and the output terminal of the OR gate G is connected to the first oscillation circuit 2a.

When only the audio track TRa shown in Fig. 3 is erased and so-called after recording is performed, the power from the first power supply terminal Ia is
is inputted to the first oscillation circuit 2a via the gate G,
Only the audio erasing head Ha is operated by the oscillation signal from the first oscillating circuit A2, and after erasing only the audio track, so-called after-recording is performed by the recording/reproducing head Hc.

Therefore, according to the embodiment described above, when performing so-called after-recording, only the audio erasing head Ha can be operated and only the audio track can be reliably erased. No need to install a coil,
It is possible to reduce power consumption and to have an inexpensive circuit configuration.

As described above, according to the video tape recorder erasing circuit of this invention, the audio erasing head and the full-width erasing head are operated by oscillation signals from separate oscillation circuits, reducing power consumption and achieving an inexpensive circuit configuration. It is something that can be done.

[Brief explanation of the drawing]

FIG. 1 is a wiring diagram of a conventional erasing circuit for a video tape recorder, and FIGS. 2 to 7 show embodiments of the erasing circuit for a video tape recorder according to the present invention.
Fig. 2 is a wiring diagram of one embodiment, Fig. 3 is an operation explanatory diagram of Fig. 2, Fig. 4 is a wiring diagram of another embodiment, Fig. 5 is a configuration explanatory diagram of a part of Fig. 4, FIG. 6 is an explanatory diagram of the operation of FIG. 4, and FIG. 7 is a wiring diagram of still another embodiment. 2a, 2b...first and second oscillation circuits, A1, A
2, A3...control circuit, Ha...audio erasure head,
Hb...Full width erase head, Ia, Ib...1st, 2nd
Power terminal.

Claims (1)

[Scope of utility model registration request] An audio erasing head for erasing an audio track of a videotape, a full-width erasing head for erasing all tracks of a videotape, a first oscillator circuit for driving the audio erasing head, and a second oscillator circuit for driving the full-width erasing head. a first power supply terminal for supplying power to the first oscillation circuit during audio recording; a second power supply terminal for supplying power to the second oscillation circuit during normal recording; and a power supply from the second power supply terminal. and a control circuit for supplying power to the first oscillation circuit for a predetermined period at the start of the normal recording.