JVC M-7050 - Adjustment Procedures

ADJUSTMENT PROCEDURE OF AMPLIFIER
Adjustment procedures
Left channel—— |-—Right channel
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Note:
Before turning on the power, turn R625 of left and right channels to middie point
and R411, 412, R732, R732 fully counter-clockwise.
Fig. 11.
Idling current adjustment of the power amplifier
(TAD-279C)
As illustrated in Fig. 11. take voltage readings between the
testpointsof A-B, A-C, A-D, A-E, F-G, F-H,F-
J, F-K with DC millivoltmeters. (Turn on the power switch
and wait for 5 minutes and then start the adjustment) First,
turn R731 fully counterclockwise and then turn it clockwise
slowly while watching the DC millivoltmeter connected bet-
ween A-B in order to adjust the current value to 50 mV.
Similarly, connect the DC millivoltmeters between A-C, A-
D, A-E, F-G , F-H, F-J, F-K and confirm that
these meter read 40-60 mV. (The idling current becomes
80-120 mA). If the millivoltmeters do not read 80 —
120 mA, turn R731 slightly for adjustment.
Adjustment of the power output meter
Before turning on the power, set R411, 412 to middle point.
Adjust R411(left), R412(right) so that the output power
meter shows 150 W point when output power is 34.7 V on
speaker terminal.
13
Adjustment of the offset voltage of the power
amplifier (TAD-279C)
Before
turning
on
the
power,
turn
R625
of
left
and
right
channels
to
middle
point.
As
shown
in
Fig.
11.
connect
the
DC
millivoltmeter
between
the
testpoints
of
A
-ground,
and
then
turn
R625
slowly
so
that
the
meter
shows
as
low
a
value
as
possible,
(if
possible
“0”).
On
completion
of
the
adjustment,
wait
for
5—6
minutes,
and
confirm
whether
or
not
the
adjusted
voltage
varies
greatly.
Precautions
A
nonpolar
DC
millivoltmeter
is
preferable
for
the
above
adjustments.
If
polar
millivoltmeters
are
used,
pay
careful
attention
to
their
plus
(+)
and
minus
(—)
polarities.
Start
the
measurements
using
the
highest
meter
range.