JVC M-7050 - Page 12

Fig. 10.
5)
If
the
wrong
waveform
is
detected,
vary
the
input
voltage
from
OV
up
gradually
and
check
waveform
in
varying
voltage
ranges
of
the
oscilloscope.
if
the
right
waveform
is
not
obtained
yet,
check
transistors
and
resistors
in
the
circuits
using
a
multimeter.
The
resistors
marked
with
A\
in
the
circuit
diagram
are
liable
to
disconnection.
MEMO RUNDOM
6)
When the waveform of Fig. 10 is detected, stop
supplying power and plug the wires into the sockets
of TPS-226. Then start supplying power while you
monitor waveform at the test points with the input
voltage kept applied.
Do not connect any dummy load yet. Normally you
will see sine waves on the oscilloscope. Carry out
the above steps for both channels. At this time the
output voltage exceeds 35V. For safety, you can
raise the voltage gradually, if a varying-voltage
power transformer is available,while you watch the
waveform.
Connect a dummy load. Normally the output level
is approximately 35V over an 8-ohm load (150W)
when both channels are driven with 1-kHz input
signal.
Even if the SUPER-A block is defective, the ampli-
fier will operate in class B. In this case, check the
SUPER-A block referring to ‘3, SUPER-A block”’.
Referring to “Adjustment” (page 13), check idling
current, voltages at test points, voltage gain, and
frequency response, etc.
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