Samsung CHA4217L Service Manual page 40

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.
Check connections between
CN202 and CN202_2.
Does the PWM duty of
IC202's Pin 21 vary adjusting
ABL step?
No
Check and replace IC202 and
around parts.
7-16
Display the full white pattern.
No
Does full white luminance vary,
adjusting ABL step with Softjig?
Yes
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
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
Are 12 V line, R504, L504, Q501
and Q518 ok?
Are C509, D514, Q502 and Q506
Check and replace T501 and CRT.
Yes
Replace R121 to higher or lower
one that meets the spec.
No
No
Yes
ok?
Yes
Are full white and white
Yes
square luminance almost
same?
No
Is R121 right as CRT's
differential items?
Replace it.
Yes
Check and replace IC101.
Yes
Check and replace D518, IC101.
No
Replace it.
No
Replace it.
No
Yes
CHA42*7L/5**7L