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15
5-6 DBX PCB ADJUSTMENT
NOTES:
3. Simply press the POWER switch to ON (all other switches and
controls on the deck have no affect on this adjustment), then
make this section adjustment.
4. The measurement equipment's GND (0 V) terminal should be
connected to the dbx PCB's E terminal, except in steps 2 and 3,
and 6 to 8 in both the ENCODER and DECODER adjustments.
5-7 ADJUSTMENT AND TEST POINT LOCATIONS (2)
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Fig. 5-12
R78/R88
and R77/R87 settings
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Fig. 5-13
R78/R88
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Fig. 5-11
5-6-1 ENCODER ADJUSTMENT
1.
2.
Distortion: 0.02% or less
Output: 3V or more
16
Distortion: 0.02% or less
Output: 3V or more
Preset all adjustors approximately to the center position.
Make the Fig. 5-14 connections, then feed 100 Hz, —8 dB (308 ,
mV) to A/C (INPUT) terminal.
. Adjust R78/R88 to obtain a clear 200 Hz sine-wave on the oscil-
loscope. See Fig's 5-12 and 5-13.
. Change the connections to Fig. 5-15, then feed a 1 kHz/—8 dB
(308 mV) input signal to the INPUT terminal. Adjust R76/R86
so that AC voltmeter reads —8 dB (308 mV).
. With the conditions in step 4, adjust R74/R84 for minimum dis-
tortion (0.1% or less).
. Like Fig. 5-16, connect a DC voltmeter between TP1 and TP9
for L-ch (or TP3 and TP11 for R-ch), then note the reading on
the DC voltmeter with an input signal of 1 kHz/—8 dB (308 mV).
. Cut off the input signal, then make the same measurement as
in step 6 to adjust R75/R85 for the same level.
Low distortion
AF OSCILLATOR
10.
11.
. Repeat above steps 5 to 7 until the best results are obtained.
. Check that when the input signal is 100 Hz/—8 dB (308 mV),
then 10 kHz/—8 dB, the output signal from B/D (OUTPUT)
terminal deviates.by +0.5. dB +0.5 dB, then —2.8 dB +0.5 dB
from —8 dB (reference), respectively ... so that output, as a
voltage value, should be 308 mV to 346 mV for 100 Hz, and
211 mV to 237 mV for 10 kHz.
Check that when 1 kHz/—-68 dB (308 pV) is applied, the output
is —38 dB +0.5 dB (9.21 mV to 10.3 mV).
Check that when the input signal is 1 kHz, +12 dB (3.08 V), the
output is +2 dB 40.5 dB
(0.921V to 1.03V)
and distortion
factor is 0.3% or less.
OSCILLOSCOPE
AC VOLTMETER
ATTENUATOR
DBX
PCB
T.P10
(T.P12)
T.P9
(T.P11}
Fig.5-14
Connections for ENCODER adjustment (1)
Low distortion
AF OSCILLATOR
© A(C)
| DBX
PCB
|
(D)O
NOTE: Leh (Reh)
AC VOLTMETER
OSCILLOSCOPE
DISTORTION
ad
METER
Fig. 5-15
Connections for ENCODER adjustment (2)
Low distortion
AF OSCILLATOR
ATTENUATOR
© A(C)
Distortion: 0.02% or less
Output: 3V or more
DBX
PCB
T.P1
(T.P3)
TPS
#23v 1
G
(T.P 11)
|
DC VOLTMETER
NOTE: Lch (Reh)
Fig.5-16
Connections for ENCODER
adjustment (3)
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