Sharp SX51LF7 Service Manual page 27

TROUBLE SHOOTING TABLE
CIRCUITS TO BE CHECKED:
» Tuner.
» PIF.
» Automatic Gain Control.
» (5V), (32V) Power Source.
Noise increases but no signal is
received.
Check the tuner supply voltage LB and
HB must be approx. 5V. BT must be
approx. 32V. and CH preset data check.
Check the tuner AGC at
TP201.
Check pin(38) of
IC801.
CIRCUITS TO BE CHECKED:
» Sound Detector Circuit.
» Sound Switch and Att.
Control.
» Audio Output Circuit.
NO PICTURE, NO SOUND
Does the noise level increase at max.
Contrast, Brightness and Sound controls ?
Check pin (27) of
IC801, Tuner and
related circuit.
NO SOUND
Does noise signal appear at
pins (3) and (22) of IC305 ?
Does signal appear at pins
(2) and (5) of IC302 ?
Check IC302 and
Check Speaker.
peripheral circuit.
(Continued)
Does noise or signal appear at pin (40)
of IC801 ?
Does noise or
signal appear at
pin (38) of IC801 ?
Does noise or
signal appear at
pin (23) and (24)
of IC801 ?
Check pin (1) of
SF201, Tuner and
related circuit.
Check TV sound.
Is there audio signal at pins (3)
and (5) of SC2300?
(NICAM/IGR unit socket)
Check IC401.
*NOTE:
NICAM/IGR for model
SX51LF8 Only IGR for
model SX51LF7 Only.
27
SX51LF7
SX51LF8
No snow noise.
Check IC801 and
its related circuit.
Check IC401 and
related circuit.
Check pin (37)of
IC801 and related
circuit.
Check NICAM/
IGR unit, tuner
and its peripheral
circuit.