JPS6115490B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic adjustment method for a tape recorder, and its purpose is to automatically adjust the overall frequency characteristics of a tape recorder to an optimal state correctly, reliably, and quickly. .

Adjustment of the overall frequency characteristics of conventional tape recorders currently relies on manual labor, and the adjustment takes a considerable amount of time. Moreover, the quality of the adjustment largely depends on the level of skill and intuition of the adjuster, and it has been extremely difficult to eliminate variations in the adjustment results.

The present invention is intended to eliminate such conventional drawbacks, and one embodiment thereof will be described below with reference to the drawings. Before explaining the example, generally speaking, the playback output of a tape recorder has a constant frequency,
Even if the signal is at a constant level, it fluctuates as shown in FIG. Particularly, slight peeling of the magnetic material on the magnetic tape and adhesion of dust to the tape during playback may cause partial loss of output, so-called dropout, and large level fluctuations (A and B in FIG. 1). Therefore, in order to find the optimal value of the bias current as a variable for adjusting the overall frequency characteristics of the tape recorder, the bias current value determined by continuously changing the value for a short period of 2 to 3 seconds is as described above. The optimum value is often not achieved due to dropout. Such an unstable adjustment method is particularly inappropriate for mass production, and causes frequent adjustment errors.

The adjustment method of this embodiment solves these conventional problems and enables automatic adjustment. First, Figure 2 shows an automatic adjustment device for a tape recorder that realizes this adjustment method, where 1 is the tape recorder to be adjusted, 2 is its operating mechanism, and 3 measures the playback output level from tape recorder 1. 4 is a computer-configured central processing unit (so-called CPU) that processes the measurement result output from the measurement circuit 3; 5 is a motor 6 for adjusting the tape recorder's operation mode and bias current according to the calculation output from the CPU 4; This is a control circuit that controls the

Next, an adjustment method using a device having such a configuration will be explained. First, the tape recorder 1 is put into a recording state and an adjustment signal is recorded. As shown in Figure 3, this adjustment signal is a mark signal for detecting the recording start position, so-called cueing during playback, and two different frequencies f ₁ and f ₂ that define the frequency characteristics, for example 1KHZ. It consists of a signal mixed with a 10KHZ signal. The recording format is to first record the above adjustment signal for T time with the bias current value set to _I1 , and then turn the motor 6 to record the bias current value, which is different from the above _I1 .
The above adjustment signal is recorded for a time T with the bias current value set to _I2 . After this series of recording is completed, the control circuit 5 automatically rewinds the tape and brings it into playback mode. In this playback state, first, the mark signal is detected and the cue is searched, and the input signal filter of the measuring circuit 3 is set to f1 _.
(1KHZ) and read the playback output level. Next, set the above filter to f ₂ (10KHZ) and read the playback output level. Figure 4 shows the reproduced output of only the frequency f _1. This reproduced output changes as shown in the figure, including dropouts a to d, and the reproduced output changes depending on the different bias current values I ₁ and I ₂ . _D1 ,
D will have _two different values. The reproduced output of only the frequency _f2 shows a similar change. Therefore, now, the playback output at bias current value I ₁ at frequency f ₁ is D ₁₁ d _B , I ₂
Let the output at I ₁ and I ₂ at f ₂ be _{D 21 and} D ₂₂ d _{B ,} respectively. As shown in Figure 5, when adjusting the frequency characteristics so that f ₂ becomes Ld _B with respect to f ₁ , the frequency characteristics change linearly in the vicinity of the bias current value I at which Ld _B is obtained. (The dotted curve in FIG. 5 indicates the variation in characteristics.) Therefore, the following empirical formula holds true for the bias current value I to be determined. That is, I=I ₁ + (I ₂ - I ₁ ) x L ₁ - L/L ₁ - L ₂ ... (1) where, L ₁ = D ₁₂ - D ₁₁ ... (2), L ₂ = D ₂₂ -D ₂₁ …(3)
, and I ₁ and I ₂ are two bias current values located above the average bias current value I obtained from the above Ld _B. In addition, the above playback output level D ₁₁ ,
D ₁₂ , D ₂₁ , and D ₂₂ are determined by measuring the output corresponding to I ₁ n times, for example, 11 times, in order to avoid the effects of dropouts a to d shown in Fig. 4, and calculating the measurement result values.
The values are arranged in descending order within the CPU 4, and the second to fourth values are averaged and determined by decibel conversion. As is clear from the adjustment flowchart in Figure 6, the reproduction output at two different bias current values I ₁ and I ₂ is measured twice, the average value is calculated in the CPU 4, and the values D ₁₁ and D ₁₂ are calculated. , D ₂₁ , and D ₂₂ are determined. Based on the determined values, L ₁ and L ₂ are further determined in the CPU 4 according to the above formulas 2 and 3, and I is determined according to formula (1). The control circuit 5 controls the rotation of the motor 6 to obtain the determined bias current value I, and adjusts the variable inductance that constitutes the bias oscillation circuit in the tape recorder 1. The automatic adjustment operation ends when the bias current value reaches I, and the overall frequency characteristic becomes optimal.

As explained above, according to the tape recorder automatic adjustment method of the present invention, the overall frequency characteristics of the tape recorder can be automatically adjusted correctly and in a short time without being affected by dropout.
Adjustment work can be made easier and variations in adjustment can be minimized.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the playback output of a general tape recorder, FIG. 2 is a configuration diagram of an automatic adjustment device implementing the automatic adjustment method for a tape recorder of the present invention, and FIG.
Figure 4 is a diagram showing the adjustment signal, Figure 4 is a diagram showing the adjustment signal playback output of the tape recorder, Figure 5 is a diagram showing the relationship between bias current and frequency characteristics, and Figure 6 is a diagram explaining the flow of automatic adjustment. It is. DESCRIPTION OF SYMBOLS 1...Tape recorder, 2...Operation mechanism section, 3...Measuring circuit, 4...CPU, 5...Control circuit.

Claims (1)

[Claims] 1. The tape recorder to be adjusted has at least two
With two different bias current values I ₁ and I ₂ applied, an adjustment signal composed of a mixture of multiple frequencies is recorded for an arbitrary time for each bias current value, and this is played back to adjust the playback level to each of the above. Measure the portion corresponding to the bias current value multiple times at each frequency, convert the measured values into decibels, average specific multiple values among the converted values, and calculate the difference between the average values at each frequency as described above. Bias current value I ₁ ,
Assuming that the overall frequency characteristics at I ₂ are L ₁ and L ₂ , the bias current to obtain the desired adjustment value L is determined by the formula I = I ₁ + (I ₂ - I ₁ ) x L ₁ - L/L ₁ - L ₂ . An automatic adjustment method for a tape recorder that calculates the bias current value I and adjusts the bias oscillation circuit of the tape recorder so that the bias current value I is obtained.