Technics RS-646DS-D

13
Overall frequency response
Equipment:
* VIVM
* AF oscillator
+ ATT
* Test tape
(reference blank tape)
+++ C-RA for Normal
+++ C-RF for CrOz
Overall frequency response
(As a standard for adjustment)
MEASUREMENT & ADJUSTMENT
Note:
Before measuring, and adjusting, make sure of the playback frequency
response (For the method of measurement, please refer to the playback
frequency response).
1. Test equipment connection is shown in fig. 19.
2. Load reference blank test tape and place UNIT into record mode.
3. Supply 1 kHz signal from AF oscillator through ATT to LINE IN.
4. Adjust ATT so that input level is —20dB below standard recording
level (standard recording level = 0 VU).
. At this time, LINE OUT level indicates 0.042 V.
. Record each frequency 40 Hz, 100 Hz, 200 Hz, 500 Hz, 1 kHz, 2 kHz,
3kHz, 10kHz, 12kHz and 13kHz at the same level.
. Playback and express in dB the difference between playback output
level of each frequency based on playback output level of 1 kHz.
. Make sure that the measured value is within the range specified in
the overall frequency response chart.
. Set the bias selector to “HIGH”, and the EQ. selector to “70S”.
. Measure as same as manner above.
. Make sure that the measured value is within the range specified in
the overall frequency response chart (See fig. 23).
Overall frequency response chart (Normal & CrO2)
A.SKHz 2KHz
12KHH 7.948
Adjustment 1—Using bias current
1. When the frequency response between the middle- and high-frequency
range becomes higher than the standard value, as shown by the solid
line in fig. 24 increase the bias current by turning L5 (-CH), L6 (R-
CH).
. When it becomes lower, as shown by dotted line, reduce the bias cur-
rent by turning L5 (L-CH), L6 (R-CH). (See fig. 28 on page 17).
oe
~ 4
Me
GLA
1KHz2 1 .5KHz 2KHz 4K
Frequency (Hz)
Fig. 24
REMARKS
* Record/playback mode
* Record level control
..» MAX
LOW
120uS
* Bias selector
* EQ. selector
(for Normal tape)
* Bias selector
* EQ. selector
(for CrOz tape)