Technics RS-B765 - Page 18

OVERALL FREQUENCY RESPONSE
1. Insert the normal blank test tape (QZZCRA) and set the
unit to the record pause mode.
2. Apply a reference input signal (1kHz, —24d8) through an
attenuator.
3. Attenuate the signal by 20dB and adjust the frequency
from 50Hz~10kHz.
4. Record the frequency sweep.
5. Playback the recorded signal and assure that it is within
the range shown in Fig. 8 in comparison to the reference
frequency (1kHz).
6. If it is not within the standard range, adjust VR301
(L-CH) and VR302 (R-CH) so that the frequency level is
within the standard range.
¢
Level
up
in
high
frequency
range
Increase
the
bias
current.
*
Level
down
in
high
frequency
range
...Decrease
the
bias
current.
7.
Repeat
steps
2~6
above
using
the
CrO,
tape
(QZZCRX)
and the metal tape (QZ2ZCRZ) increasing the frequency
range to 12.5kHz (50Hz~12.5kHz).
8.
Assure
that
the
level
is
within
the
range
shown
in
Fig.
9.
LINE IN LINE OUT
AF oscillator = ATT
OVERALL GAIN ADJUSTMENT
1. Insert the normal blank test tape (QZZCRA) and set the
unit to the record pause mode.
. Apply a reference input signal (1kHz, —24dB).
Attenuate the output so that its level becomes 0.4V.
. Record this input signal.
. Playback the signal recorded In step 3 above, and assure
that the output is within the standard value.
. If it Is not within the standard value, adjust VR5 (L-CH)
and VR6 (R-CH).
. Repeat the step 2~5 above until the output is within the
standard value.
Standard value: 0.4V+0.5dB
CHECKING THE EFFECT OF BIAS ADJ. VR
1. insert the Metal blank test tape (QZZCRZ) and set the
unit to the Record mode.
2. While turning the Bias Adj. VR from minimum to
maximum, verify that the output at TP1 (L-CH) and TP2
(R-CH) to ground vary more than +3.5dB.
If the output variation span is less than +3.5dB, adjust
L303 (L-CH) or L302 (R-CH) until it exceeds +3.5dB.
RS-B755
Normal Overall frequency response chart (NR OUT)
SOHz 100Hz 200Hz SOOQHz 1kHz 2kHz
Fig. 8
CrO, Metal Overall frequency response chart (NR OUT)
50Hz 100Hz 200Hz 500Hz 1kHz 2kHz
Fig. 9
12.5kHz
LINE IN LINE OUT
EVM Oscilloscooe