Read LG 42LG72 (CHASSIS:LA86B) Service Manual online
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Yes
(4) Component
Check JK700, JK702.
Can you see the normal waveform?
Check the input and output of BCM355x (IC100).
Measure waveform at C638, C639, C640 and C628,
C629, C630 because it’s more easy to check
Can you see the normal waveform?
JK700, JK702 may have problem.
Replace this Jack.
No
This board has big problem because Main chip
(BCM355x) have some troubles.
After checking thoroughly all path once again,
You should decide to replace BCM355x or not.
Yes
Yes
(5) RGB_PC
Check JK705.
Can you see the normal waveform?
Check the input(Pin AK16, AN15, AM15, AH16, AJ16 of
BCM355x (IC100). Measure waveform at C635, C636,
C637 and R755, R758 because it’s more easy to check.
Can you see the normal waveform?
JK705 may have problem.
Replace this Jack.
No
This board has big problem because Main chip
(BCM355x) have some troubles.
After checking thoroughly all path once again,
You should decide to replace BCM355x or not.
Yes
Check DDC communication lines.
(IC601, IC602,IC603, IC701)
Yes
Check the output of PI3HDMI341ATR(IC600).
Can you see the normal waveform?
After checking the Power of this chip, you
should decide to replace this or not.
No
Check the input connect JK600, JK601, JK602, JK708.
Can you see the normal waveform?
Yes
JK600, JK601, JK708 may have problem
Replace this Jack.
No
Check HDCP communication lines. (IC102)
Yes
After checking the Power of this chip, you
should decide to replace this or not.
No
This board has big problem because Main chip
(BCM355x) have some troubles.
After checking thoroughly all path once again,
You should decide to replace BCM355x or not.
No
(6) HDMI
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