Technics RS-630USD

Overall frequency response
(As a standard for adjustment)
Overall S/N ratio
Equipment:
* VTVM
* AF oscillator
* ATT
* Oscilloscope
* Test tape
(reference blank tape)
“CRA
Dolby NR circuit
Equipment:
+ VTVM
* AF oscillator
* ATT
* Oscilloscope
13
es
MEASUREMENT & ADJUSTMENT
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 figure 26, increase the bias current by turning L5 (L-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).
Note:
1. For adjustment when the bias current is lower than the standard value
0.17 mA, use the procedure indicated in adjustment 2, because reduc-
ing the bias current beyond this point may worsen the distortion factor.
2. For the method of bias current measurement, refer to “Bias Current
Adjustment” on page 9.
Adjustment 2-Using the peaking coil for recording equalization
UwHZ 2aHe 3kHz 1OwHZ UI kHz
Fig. 27
When the frequency response is flat in the middle-frequency range and
makes a sharp rise or drop in the high-frequency range, as shown in
fig. 27, adjust by turning the peaking coil 3 (L-CH), L4 (R-CH) for
normal tape recording equalization.
. Test equipment connection is shown in fig. 19.
2. Supply 1kHz signal to LINE IN and adjust ATT so that output level
at LINE OUT indicates 0.42 V (— 7 dB).
. Make recording.
. Make another recording without supplying signal (disconnect input plug
to: LINE IN).
. Rewind to recorded part and playback.
. Measure output signal level and no signa! level (noise), and determine
the ratio in decibels (dB).
. The value is difference between “Playback S/N and overall S/N’, but
for decibel calculation refer to “Playback S/N measurement” on page
8.
Standard Value: Greater than 40dB
(without NAB filter)
REMARKS
* Record/playback mode
* LINE IN level control
--MAX
* Erase the tape with a
bulk tape eraser.
* Input selector---LINE IN
1. Place UNIT into record mode, set the Dolby NR switch to OUT posi-
tion and supply to LINE IN to obtain —34.5dB at TP3 (L-CH), TP4
(R-CH) (frequency 5 kHz).
. Confirm that the value at IN position is 8dB greater than the value at
OUT position of Dolby NR switch.
. When it is not in condition above, adjust as follows.
. Set VR7 (L-CH), VR8 (R-CH) to maximum.
. Set the Dolby NR switch to IN position.
_ At this time adjust VR9(L-CH), VR10 (R-CH) so that the reading of
VTVM become 10-dB greater than the value in step (1) above.
. Adjusting VR7 (L-CH), VR8 (R-CH), make the reading of VTVM be-
come 2dB smaller than the value obtainted through the adjustment
in step (6) above.
* Record mode
* LINE IN level control
...MAX
* Input selector---LINE IN