Tascam 388 Studio 8 - Decoder

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1-6-4. Decoder
Apply Low signal to J111-2 to actívate DBX
Decode moda.
A. RMS Symmetry Adjustment (Connectlon: Fig.
1-6-2)
1. Apply a 100 Hz, 300 mV signa! to J110-1
terminal.
2. Adjust R135 to obtain a olean 200 Hz sine-
wave on TP01 (sea Figs. 1-6-5 & 1-6-6).
B.VCA Symmetry Adjustment (Connection:
Fig. 1-6-4)
1. Apply a staircase wave signa! to TP01 , and a
traingle wave signa! to the horizontal input
terminal on the oscilloscope.
2. Shortcircüit between J110-1 and J110-2.
3. Adjust R118 for a relatively straight hori
zontal lina display on the oscilloscope.
(Leve! deviation: 5 mV or less)
C. Decoding Leve! (Connection: Fig. 1-6-2)
1. Apply a 1 kHz, 300 mV signa! to J110-1
terminal.
2. Adjust R107 for a 300 mV reading atJ 110-5
terminal.
D.Frequency Response (Connection: Fig. 1-6-2)
1. Vary the signa! frequency to 50 Hz (300 mV)
and then to 10 kHz (300 mV).
2. Read the output leve! at the J110-5 terminal
for each frequency. The output leve! should
be within the following limits with reference
to leve! at 1 kHz.
50 Hz: +5 dB ± 1 dB (447 mV to 602 mV)
10 kHz: +9.4 dB ± 1 dB (793 mV to 997 mV)
5. Ralease Rata Check (Connection: Fig. 1-6-3)
Q ^ ^ burst wave signa! with
o cycles on and 128 cycles off.
■ + ?n ralease rata is less than 750 mV
F. Decode Effect Check (Connection: Fig. 1-6-2)
'•^PP'y a 1kHz, -20dB signa! to J110-1
terminal
2. Confirm that the leve! at J110-5 terminal is
-300 dB ±0.5 dB (i.e., -20 d8 against -10 dB
(300 mV) reference level).
3. Apply a 1 kHz, O dB signa! to J110-1 terminal.
4. Confirm that the level at J110-5 terminal is
+10 dB ±0.5 dB (i.e., +20 dB against -10 dB
(300 mV) reference level).
G.Other Channeis
Repeat procedures for channeis
8 using the following adjustment
input/output termináis.
2 through
points and
Channel
Decode mode
L signal
Input Output Test Point
Adjustment Point
RMS
VCA
Level
ch1/ch5
J111-2
J110-1 J110-5 TP01 R135 R118 R107
ch2/ch6 J2n-2 J210-1 J210 5 TP02 R235 R218 R207
ch3/ch7
J311 2
J3101 J310-5 TP03
R335 R318 R307
ch4/ch8 J4n-2
J410-1
J410-5
TP04
R435 R438 R407
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