Teac A-7300RX - Encoder Operation

dbx PERFORMANCE
The
A-7300RX
dbx
performance
ENCODER
and
DECODER
adjustments
themselves
are
critical
and
should
only
be
performed
by
skilled
technicians.
10-25
PREPARATION
NOTE:
Prior
to
doing
the
dbx
system
adjustment
proce-
dure
the
output
voltage
of
the
Stabilizer
Unit
B
must
be
checked
and
adjusted
if
necessary.
Adjust
VR-171
for
+15
V
at
Test
Point
(terminal)
No.
8.
Confirm
also,
that
the
output
of
Test
Point
No.
1
is
—15
+0.5
V.
@ VR-17
Fig. 10-19 Stabilizer Unit B Adj. Location
MONITOR
SW
.........
SOURCE
Input Selector SW......... LINE
Apply
a
400
Hz
signal
at
~8 dB
(308
mV)
to
the
LINE
IN
jacks.
Adjust
LINE
controls
for
—8
dB
(308
mV)
at
SOURCE/
TAPE
output
jacks.
With
controls
set
as
described
above
in
MONITOR
LEVEL
SETTING
10-10
begin
following
checks
and
adjustments.
10-26
ENCODER
LEVEL
ADJUSTMENT
1.
Apply
a
1
kHz
signal
at
—8
dB
(308
mV)
to
the
LINE
IN
jacks.
Check
for
—1
dB
(690
mV)
approx.
at
ENCODER
output
jacks.
2.
Depress
and
release
the
ENCODER
pushbuttons
(IN
and
OUT).
Check
that
change
in
level
is
0.5
dB
or
less.
3.
Adjust
VR-814
(LEVEL
ADJ.
VR)
if
necessary,
to
‘ob-
tain
this
reading.
NOTE:
Input
impedance
of
the
VTVM
used
in
this
Test
must
be
1
M
ohm
or
more.
26
10-27 ENCODER OPERATION CHECK
With controls set as described above in Section 10-25,
10-26 step 1 and set ENCODER SW to IN. -
1.
Change the Input frequency to 100 Hz,
The ENCODER output level should read —3.5 dB £0.5
dB (548 mV— 488 mV).
. Change the Input signal frequency to 10 kHz,
The ENCODER output level should read —5.7 dB +0.5
dB (435 mV— 388 mV).
. Decrease input level to —58 (975 mV) dB and check that
ENCODER output level reads —26 dB +0.5 dB (36.6
mV—41.1 mV).
. Increase input level to +12 dB (3.08 V) and check that
ENCODER
output
level
reads
+9
dB
+0.5
dB
(2.06
V—
2.30
V).
. With these condition distortions should be less than
0.5%.
. Change the Input signal frequency to 19 kHz (£5%) and
set the MPX SW to IN position.
. The ENCODER output level should read —26 dB (38.8
mV) or less.
. Change the Input signal frequency to 38 kHz to LINE
IN jack. The ENCODER output level should read —9 dB
(274 mV).
. Remove input signal and check that ENCODER output
noise level is —40 dB or less.
10-28 DECODER LEVEL SET
1.
2.
Change the Input signal frequency to | kHz to LINE IN
jacks.
The SOURCE/TAPE output should read ~8 dB (308
mV).
. Depress and release the SOURCE MONIFOR SW push-
button (NORMAL and DECODER).
. Check that change in level is +1 dB or less,
. Adjust VR-624 (LEVEL ADJ. VR) if necessary, to ob-
tain this reading.