Sharp 21HM-10F, Service Manual

Page: 22 / 32

37
21HM-10F
TROUBLESHOOTING TABLES.
NO PICTURE, NO SOUND
CIRCUITS TO BE CHECKED:
Tuner.
PIF.
Does the noise level increase at max.
Automatic Gain Control. Contrast,Brightness and Sound controls?
5V, 32V Power Source.
Noise increase but no No snow noise.
signal is received.
Check the tuner supply voltage Does noise or signal appear
LB and HB must be approx. 5V, at pin40 of IC801?
BT must be approx. 32V,and NO YES
CH preset data check.
Does noise or Check IC801
signal appear at and its related
Normal
pin38 of IC801? circuit.
NO YES
Check the tuner Does noise or
AGC at TP201. signal appear at Check Q401
pin23 and 24 Q402 and related
Normal Abnormal
of IC801? circuit.
NO YES
Check pin38 Check pin27 Check pin
2,4
of
of IC801. of IC801,Tuner
(SA)
,Tuner Check pin37 of
and related circuit. and related IC801 and
circuit. related circuit.
NO SOUND
CIRCUITS TO BE CHECKED:
NO
Audio Output Circuit. Does signal appear Check IC801 and
at pin6 of IC303? its related circuit.
YES NO
Check Speaker. Check IC303 and
peripheral circuit.