Sharp 21GT-22, Service Manual

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16-1
16-2
16
21GT-22
TROUBLE SHOOTING TABLE
(Continued)
NO PICTURE, NO SOUND
Does noise signal appear at pin (44) of IC801 ?
NO SOUND
No snow noise.
Does noise or signal appear at pin (40) of IC801 ?
Noise increases but no signal is received.
Check the tuner supply voltage LB must be approx. 5V, BT must be approx. 32V. and CH preset data check.
Check the tuner AGC at TP201.
Does noise or signal appear at pin (38) of IC801 ?
Check IC801 and its related circuit.
Check pin (1) of SF201, Tuner and related circuit. Check pin (37) of IC801 and related circuit.
Check Q253, Q254 and related circuit.
Check IC801.
Check C356 and peripheral circuit.
Check pin (27) of IC801, Tuner and related circuit.
Check pin(38) of IC801.
Does the noise level increase at max. Contrast, Brightness and Sound controls ?
CIRCUITS TO BE CHECKED:
»
Tuner.
»
PIF.
»
Automatic Gain Control.
»
(5V), (32V) Power Source.
CIRCUITS TO BE CHECKED:
»
Sound system pins (28)
and (44) of IC801.
»
Sound Detector Circuit.
»
Sound Switch and Att.
Control.
»
Audio Output Circuit.
Does signal appear at pins (2) and (4) of IC301 ?
Check P302, IC301 and peripheral circuit.
Check Q321, pins(4) and (6) of IC801 and peripheral circuit.
Does signal appear at pins(28) of IC801?
TROUBLE SHOOTING TABLE
(Continued)
NEITHER VERTICAL NOR
HORIZONTAL SYNCHRONIZATION
CIRCUIT TO BE CHECKED:
»
Sync. Separator Circuit.
NO VERTICAL SCAN
Vertical linearity and size abnormal.
Check pins(16), (17) and (34) of IC801.
DEFECTIVE VERTICAL AMP.
AND VERTICAL LINEARITY
Readjust vertical size. (Bus Data)
Check IC501.
Check C505 and C509.
Check IC501 bias.
Check R501, R521, R503, R512, R533 and C533.