Publicidad
Idiomas disponibles
Idiomas disponibles
Bees 740he)
™@ MEASUREMENT AND ADJUSTMENT METHODES
VR3, 4
Overall gain adj. S
VR3
=VR2
VR301, 302
Bias current adj. <4
TP1
Measurement Condition
einput level controls; Maximum
¢ Balance controls; Center
eTape select switch; Normal
Dolby NR switch; Out
Measuring instrument
© EVM (Electronic Voltmeter)
Oscilloscope
¢ Digital frequency counter
© AF oscillator
Test tape
¢Head azimuth adjustment (8kHz, —20dB); QZZCFM
Tape speed adjustment (3kHz, —10dB); Q2ZCWAT
* Playback frequency responce (315Hz, 12.5kHz,
10 kHz, 8kHz, 4kHz, 1kHz, 250Hz, 125Hz, 63Hz,
—20dB); QZZCFM
Head azimuth adjustment
Tape speed
adjustment VR
VR1, 2
7 Playback gain adj.
(Motor)
TP2
¢Make sure heads are clean
Make sure capstan and pressure roller are clean.
e Judgeable room temperature 20+5°C (68+9°F)
e ATT (Attenuator)
¢DC voltmeter
e Resistor (600Q)
¢ Playback gain adjustment (315Hz, 0dB); QZZCFM
¢ Overall frequency response, Overall gain adjustment
«Normal reference blank tape; QZZCRA
* CrO, reference blank tape; QZZCRX
¢ Metal reference blank tape; QZZCRZ
1. Test
equipment
connection
is shown
in *od/Playback Head
Fig. 1.
2. Playback
the azimuth
adjusted
part (8kHz,
—20dB)
of the
test
tape
(QZZCFM)
and
regulate the angle adjusting screw so that
the outputs of L-CH and R-CH are maximized.
(When the adjusting positions are different
with L-CH and R-CH, find a position where the
Azimuth Screw
Fig. 2
outputs of L-CH and R-CH are balanced, and then make the adjustment.)
. At the same time, draw a lissajous waveform and eliminate phase deflection.
Tape speed adjustment
1. Test equipment connection is shown in Fig. 3.
2. Playback the middle part of the test tape (QZZCWAT).
3. Adjust the VR in the motor so that the output is within the standard.
Standard value: 3000+ 20Hz
Playback frequency response
. Test equipment connection is shown in Fig. 4.
Digital frequency
counter
. Playback
the playback frequency response part (315Hz,
12.5kHz~63 kHz, —20dB) of the test tape (QZZCFM).
. Chech that the frequency is within the range shown in
Fig. 5 for both L-CH and R-CH.
LINE OUT
SOHz
100Hz 200Hz
S500Hz
1kHz
2kHz
5kHz
10kHz
Fig. 5
Playback gain adjustment
1. Test equipment connection is shown in Fig. 4.
2. Playback the playback gain adjusted part (315Hz, OdB) of the test tape (QZZCFM).
3. Adjust VR1, (L-CH) {VR2 (R-CH)} so that the output is within the standard.
Standard value: 0.4+.0.5dB (0.02V)
Bias current adjustment
1. Test equipment connection is shown in Fig. 6.
2. Set the tape selector switch to the normal position.
3. Insert the normal tape.
4. Press the record and pause buttons.
5. Minimize the input level control and adjust VR301 (L-CH) {VR302 (R-CH)}
so that the output between TP1 (L-CH) {TP2 (R-CH)} and ground is within
the standard.
. After that check in the same way as for CrO, and metal tape.
9V (Normal)
Reference value: 14V (CrO.)
17 V (Metal)
Overall frequency response
. Test equipment connection is shown in Fig. 7.
LINE IN
LINE OUT
. Set the tape selector switch to the normal position.
. Set a normal
blank tape (QZZCRA) and record by applying
oF
=
signal (50Hz, 100Hz, 200Hz, 500Hz, 1kHz, 4kHz, 8kHz and
&
HO 00
10kHz), 20dB attenuated from the reference input level signal
"* »sctlator
(1kHz, —24dB).
. Playback the signal recorded in step 3, and check that the
level of each output frequency is within the range shown in
Fig. 8 in comparison with the reference frequency (1kHz).
. If it is not within the standard range, adjust the bias current by VR301 (L-CH) {VR302 (R-CH)} so that the
frequency level is within the standard.
« Level up in high frequency range
Increase the bias current.
* Level down in high frequency range
Decrease the bias current.
. After that increase the signal recorded on CrO, blank tape (QZZCRX) and metal blank tape (QZZCRZ) up to
12.5kHz and adjust in the same way as mentioned above and check that the frequency level is within the
range shown in Fig. 9.
+f
+468
+208
0dB
—20B
40B
60B
63Hz 100Hz 200Hz:
500Hz2 1kHz
2kHz
4kH2
8kHz 12.5kHzZ
315Hz
Fig. 8
Fig. 9
SOHz 100HzZ 200Hz
SOOHZ
1kHz
2kHz2
5SkHz 10kHz
Overall gain adjustment
. Test equipment connection is shown in Fig. 7.
. Set the tape selector switch to the normal position.
. Set a normal blank tape (QZZCRA) and apply the reference input level signal (1kHz, —24dB) in record pause
mode.
. Adjust the output 0.42V by attenuator and then record.
. Playback the signal recorded in step 3, and check that the output is within the standard.
. If it is not within the standard, adjust VR3 (L-CH) {VR4 (R-CH)} and repeat the step (2), (3) and (4) until the
output is within the standard.
Standard value: 0.4V+0.05V
Publicidad
