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4. Adjustment at '"'OdB"'.
A. Adjust the ATT so that the output level at LINE OUT becomes 0.4V.
(The input level at this condition is called the standard input level).
. Adjust ATT and check that all segments of the FL meter lights up when an
0dB
Dolby NR circuit
Condition:
Equipment:
e Record mode
eVTVM
e AF oscillator
e Dolby NR switch...IN/OUT
e ATT
¢ Oscilloscope
¢ Dolby NR select switch...B/C
—* Resistor (6002)
e Input level controls...
MAX
¢ Balance control...Center
Record side
e Check of the Dolby-B type encoder characteristics
. Make connections as shown in fig. 18.
. Set the unit to the record mode. (NR select switch is OUT.)
. Apply a 1kHz signal to LINE IN.
. Adjust the ATT so that the output level at TP3 (L-CH) and TP4 (R-CH) is 12.3mV.
. The output level at pin 21 should be OdB.
. Set the NR select switch to B, and make sure that the output signal level at pin 21 of IC3 (L-CH) and 1C4 (R-CH) is
7.
8.
e Check to Dolby-C type encoder characteristics
u.
10.
11.
12.
©
+6dB+2.5dB.
Set the NR select switch to OUT, and adjust the frequency to
5kHz. The output signal level at pin 21 should be OdB.
ue, Peak
Set the NR select switch to B and make sure that the output signal
acded niodes.7
level at pin 21 of IC3 (L-CH) and IC4 (R-CH) is +8dB+2.5dB.
3
Repeat steps 1-5 above.
Set the NR select switch to C and make sure that the output signal
level at pin 21 of 1C3 (L-CH) and IC4 (R-CH) is +11.5dB+2.5dB.
Set the NR select switch to OUT and adjust the frequency to 5kHz.
The output signal at pin 21 should be OdB.
IC4 (R-CH)
Set the NR select switch to C and make sure that the output signal
level at pin 21 of IC3 (L-CH) and IC4 (R-CH) is +8.5dB+2.5dB.
Fig. 18
AF oscillator
VTIVM Oscilloscope
Attack recovery time
Condition:
Equipment:
adjustment
e Record mode
eVTVM
(dbx circuit)
¢ Input level control... MAX
e ATT
e Balance control...Center
e AF oscillator
¢ DC voltmeter
e Noise reduction selector
...dbx tape
. Make the connections as shown in fig.19 and apply 1kHz —27dB
signal from LINE IN, and set the noise reduction selector to dbx
tape position.
. Set the unit to record mode, adjust ATT so that the signal level at
C541 (L-CH) and C542 (R-CH) is 300mvV.
. Read voltage on DC volt meter.
Reference value: 15+0.5mV
AF
has ag =e
VTVM oscilloscope
. If measured value is not within reference, adjust VR501 (shown in
electrical parts location).
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