Sharp 20GT-15, Service Manual

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20GT-15
18
TROUBLE SHOOTING TABLE
NO RASTER
Blown out.
Replace the fuse.
Check IC701, D701 and C707.
Abnormal
YES
NO
ON/OFF
ON
NO
Abnormal
Normal
The fuse is blown out again.
Does horizontal circuit
oscillate?
Check IC605, IC751 and
IC801.
D1001 (Power LED Red) turns on or turns ON/OFF.
Check T701 pin (7) voltage (Approx. 310V at 220V AC)
Check F701.
Normal
Check Secondary Main+B (Approx. 115V)
Normal
Abnormal
Normal
Check CRT connector K1-K5 bias.
Check IC801.
Checking the protector
circuit.
Check R618 and R615.
D1001 (Power LED Green) turns on.
Check D758, IC702 and
IC753.
Check R701, R707 and D709.
TROUBLE SHOOTING TABLE
(Continued)
NO PICTURE, NO SOUND
CIRCUITS TO BE CHECKED:
»
Tuner
»
PIF
»
Automatic Gain Control.
»
(5V), (32V) Power Source.
Does the noise level increase at max. Contrast, Brightness and Sound controls?
NO
YES
YES
NO
No snow noise.
Does 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 signal appear at pin (38) of IC801?
Check IC801 and related circuit.
Check IC PIF circuit and it’s related circuit.
Check Q205 and Q203 related circuit.
Check pin (27) of IC801, Tuner and realted circuit.
Check pin (38) of IC801.
YES (Signal)
NO
Does signal appear at pin (44) of IC801?
NO SOUND
CIRCUITS TO BE CHECKED:
»
Sound system pins (28), (29) &
(44) of IC801.
»
Sound Detector Circuit.
»
Sound Switch and Att. Control.
»
Audio Output Circuit.
YES
YES
NO
NO
Does signal appear at pin (6) and (8) of IC301?
Check connector IC301 and peripheral circuit.
Does signal appear at pin (28) & pin (29) of IC801?
Check
IC801.
Check C356, C359 and peripheral circuit.
Check Q301, pins (4) and (6) of IC801, and peripheral circuit.
Normal
Normal
Abnormal