SAMSUNG CHA 4217
Service Manual

7 Troubleshooting

7-2-14 ABL Failure
Symptoms : � Full white luminance is too bright. (ABL minium is over 35 F/L) � Full white luminance is too dark. (ABL maximum is under 35 F/L) � The luminance of full white and No Video are almost same.

Display the full white pattern.

Check connections between CN202 and CN202_2.

No

Does full white luminance vary, adjusting ABL step with Softjig? Yes

Yes

Are full white and white square luminance almost same? No

Does the PWM duty of IC202�s Pin 21 vary adjusting ABL step? No Check and replace IC202 and around parts.

Yes

No

Is R121 right as CRT�s differential items? Yes

Replace R121 to higher or lower one that meets the spec.

Replace it.

Does the voltage of IC101�s Pin 8 vary between full white and No Video?
F/W: 4.1~4.3V No Video: 5.3~6.0V

Yes Check and replace IC101.

No Yes Check and replace D518, IC101.

Does T501�s Pin 8 voltage vary between full white and No Video?
F/W: 1.5~3.0V No Video: 5.5~7.0V

No No

Are 12 V line, R504, L504, Q501 and Q518 ok? Yes Are C509, D514, Q502 and Q506 ok? Yes Check and replace T501 and CRT.

Replace it.

No

Replace it.

7-16

CHA42*7L/5**7L