LG FFH-3765MVA Service Manual page 11

When laser does not light.
A
Is below signal "L" at PN806
Pin (LDON)?
10
YES
Has Pick-up returned to the
innermost position?
Does pick-up stop after having
moved to the innermost position?
PN 803 LMT SW
Does fenerate about 2.4V at
IC501 Pin LD?
1
YES
Has laser power source returned
to Q501(Q501 collector voltage
about 1.8V)
YES
Flow laser current?
Both voltage of R501 is about
0.4V?
NO
Are data transferred from
NO
IC301 Pin
YES
Is below signal output at IC503
Pin
29
Does Voltage
appear at PN
YES
806 Pin
4
(LOW) & Pins
, (High)?
3 5
NO
IC552 Defective.
Are detect output input at PN806
Pin
NO
NO
NO
NO
- 2-5 -
, 93 , 94 .
91
?
YES
?
9
OPEN
CLOSE
YES
YES
R501 >> 0.4V
YES
R501 << 0.4V
NO
• IC301 Defective.
NO
• IC502, 503 defective.
• Slide motor defective.
• Connector defective.
• LMT SW defective.
• Connector defective.
• IC503 defective.
• IC501 defective.
• Surrounding circuitry defective.
• Connector defective.
• Q501 defective, connector
defective.
• Laser defective.
• Laser defective.
• Connector defective, short etc.