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6.3 LEFT OR RIGHT AMPLIFIER TROUBLESHOOTING SYMPTOMS
(Refer to Figure 6-2:
ALL VOLTAGES MEASURED WITH THE CHANNEL ON,
ACCORDINGLY, 1 kH z FREQUENCY, OUTPUT LOADED.
Check for signal presence/absences at the amplifier output pin
U400 pin 5 - Right
U401 pin 5 - Left
This should be an undistorted si new ave of approximately 80 m vR M S.
Removing the earphone (load) should cause the output level to
increase significantly.
If the
signal is present here, but not at the
possible
that
connection is missing.
as
necessary.
amplifier input pin
U400 pin 3 - Right
U401 pin 3 - Left
This
input
level
approximately 80 m vRM S. If the input signal is present here but
not present at the amplifier output pin then the amplifier may be
defective.
First check the amplifier enable line
U400 pin 1 - Right
U401 pin 1 - Left
for a
logic 0
amplifier
for
present then verify that the +5 Vdc and -5 Vdc power supplies are
present.
If amplifier enable line and power supplies check
okay, the amplifier is most likely defective.
If a logic 0 (-5 Vdc) is not present at the amplifier enable line
then check
U507 pin 16 - Right
U507 pin 19 - Left
for a logic 1 (+5 Vdc).
or U 403 Left could be defective.
accordingly.
NOTE: The U507 latch output may be loaded by a defective U4 02 or
U4 03. Remove U 402 or U403 respectfully, then recheck the control
lines
U 507 pins 16 and 19.
then U4 02 or U 403 is defective.
frequently with CMOS.
BLOCK DIAGRAM OF AMPLIFIER SIGNAL FLOW)
the
phone jack is at fault or an
Perform point-to-point connection
If the signal is not present
should
be
(-5 Vdc). A logic 1 (+5 Vdc) disables the
muting
or to conserve power.
If a logic 1 is present then U402 Right
If these voltages are
L OR R SELECTED
here,
an
undistorted
If a
Check the power supply lines
This type of error occurs
earphone it is
artwork
etch
checks
check
the
sin ew ave of
logic
0 is
out
no w correct
quite
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Troubleshooting
