21Ht-15C - Sharp 21HT-15CS Service Manual

CIRCUITS TO BE CHECKED:
Tuner.
PIF.
Automatic Gain Control.
5V, 32V Power Source.
Noise increase 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.
Normal
Check the tuner
AGC at TP201.
Normal
Check pin38
of IC801.
CIRCUITS TO BE CHECKED:
Audio Output Circuit.
NO PICTURE, NO SOUND
Does the noise level increase at max.
Contrast,Brightness and Sound controls?
signal appear at
pin38 of IC801?
signal appear at
Abnormal
Check pin27
of IC801,Tuner
and related circuit.
NO SOUND
Does signal appear
at pin6 of IC302/303?
YES
Check Speaker. Check IC302/303 and
peripheral circuit.
37
No snow noise.
Does noise or signal appear
at pin40 of IC801?
NO
Does noise or Check IC801
and its related
NO YES
Does noise or
Check Q401
pin23 and 24 Q402 and related
of IC801?
NO YES
Check pin1,2 of
SF201,Tuner Check pin37 of
and related IC801 and
circuit. related circuit.
NO
Check IC3001 and
its related circuit.
NO

21HT-15C

21HT-16C
YES
circuit.
circuit.