Technics RS-615US-D - Page 16

15
Overall frequency response
Equipment:
*VTVM
* AF oscillator
+ ATT
* Test tape
(reference blank tape)
+++ C-RA for Normal
+++ C-RF for CrO2
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. 27.
2. Load reference blank test tape and place UNIT into record mode.
3. Supply 1kHz 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 50Hz, 120Hz, 560Hz, 1kHz, 2kHz, 3kHz,
10kHz and 11kHz (12 kHz for CrO2 and EX) 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.
Overall frequency response chart (Normal)
; | |
} | |
50Hz — 125Hz 560Hz 1kHz 2kHz
Fig. 29
9. Set the tape selector to CrO2 or EX.
10. Measure as same as manner above.
11. Make sure that the measured value is within the range specified in
the overall frequency response chart for CrOz and EX tape below.
Overall frequency response chart (CrO2z and EX)
i | | |
50Hz 125Hz 560Hz 1kHz 2kHz
Fig. 30
Adjustment — Using bias current
4
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. 31, increase the bias current by turning L5 (L-CH) or L6
(R-CH) in direction of counter-clockwise ( G )
_ When it becomes lower, as shown by dotted line, reduce the bias cur-
rent by turning in direction of clockwise ( ) ).
REMARKS
+ Record/playback mode
* Record level control
-» MAX
Adjustment
stick
Increase Reduce