Teac C-3RX - DBX PCB Adjustment and Test Points

15
5-6 DBX PCB ADJUSTMENT
NOTES:
1.
This
section
adjustment
is
not
usually
needed
unless
any
of
ad-
justor(s)
have
been
changed
or
any
component(s)
on
the
PCB
have
sustained
damage,
since
both
the
ENCODER
and
DE-
CODER
sections
have
been
precisely
adjusted
in
the
factory.
2.
For
this
section
adjustment,
it
is
necessary
to
unsolder
the
wires
from
terminals
A,
C,
B,
D,
F,
1,
H,
and
J
on
the
dbx
PCB. Turn
the
deck
OFF
to
prevent
accidental
damage
when
unsoldering
or
resoldering.
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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: PEW TW WA A
é SER ERR
r4
id Fig. 5-12 R78/R88 and R77/R87 settings
iw (Incorrect)
3
o
2
w
=
3
ec
w
(=)
°
oO
w
a
DECODER Rech
RAO
a
Be
Ce
Fig. 5-13 R78/R88 and R77/R87 settings
(Correct) ‘
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)