Technics RS-B105 Service Manual page 4

RS-B105
M@ MEASUREMENTS AND ADJUSTMENTS
Adjustment point
VR3, 4
Overall gain adj.
VR301, 302
Bias current adj. <4
Measurement Condition
¢|nput level controls; Maximum
© Balance controls; Center
*Tape 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); QZZCWAT
¢ Playback frequency responce (315Hz, 12.5kHz,
10kHz, 8kHz, 4kHz, 1kHz, 250Hz, 125Hz, 63Hz,
—20dB); QZZCFM
Head azimuth adjustment
Tape speed
adjustment VR
(Motor)
¢ Make sure heads are clean
¢ Make sure capstan and pressure roller are clean.
e Judgeable room temperature 20+5°C (68+9°F)
© ATT (Attenuator)
¢DC voltmeter
¢ 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 "ecord/Playback Head Daas
Fig. 1.
2. Playback the azimuth adjusted part (8kHz,
—20dB) of the test tape (QZZCFM) and
regulate the angle adjusting screw so that
Playback gain adjustment
1. Test equipment connection is shown in Fig. 4.
2. Playback the playback gain adjusted part (315Hz, 0dB) 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
. Test equipment connection is shown in Fig. 6.
. Set the tape selector switch to the normal position.
. Insert the normal tape.
. Press the record and pause buttons.
. 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 (N
. Set the tape selector switch to the normal position.
. Set a normal blank tape (QZZCRA) and record by applying or 5
signal (50Hz, 100Hz, 200Hz, 500Hz, 1kHz, 4kHz, 8kHz and 4& IL OOG
10kHz), 20dB attenuated from the reference input level signal *F silator
(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.
LINE QUT
the outputs of L-CH and R-CH are maximized. Adimuth Screw
(When the adjusting positions are different Fig. 2
with L-CH and R-CH, find a position where the 1g.
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.
. After adjustment, lock the tape guide height and angle adjustment screws.
Tape speed adjustment LINE OUT
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+ 20 Hz
Playback frequency response
1. Test equipment connection is shown in Fig. 4.
50Hz 100Hz 200Hz SO0HZ 1kHz 2kHz 5SkHz 10kHz 5OHz 100Hz2 200Hz SO0Hz 1kHz 2kHz SkHz 10kHz
Fig. 8 Fig. 9
Digital frequency
Fi ; 3 counter .
g Overall gain adjustment
1. Test equipment connection is shown in Fig. 7.
2. Set the tape selector switch to the normal position.
3. 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
ssaah 'a
rol 2. Playback the playback frequency response part (315Hz, +408; —+4
|
12.5kHz~63kHz, —20dB) of the test tape (QZZCFM). +2¢8
3. Chech that the frequency is within the range shown in 008
Fig. 5 for both L-CH and R-CH. 248
LINE OUT
63Hz 100Hz 200Hz } 500Hz tkHz 2kHz 4kHz 8kHz 12.5kHz
315Hz
Fig. 5