LG 47LH90 Service Manual page 45

LH40/LH55 Trouble shooting guide – RGB PC
Check JK1201
Can you see the normal waveform?
YES
Check the input (Pin K1,K2,K3,L1,L3)
of LGE3159(IC100).
Measure waveform at C113,C114,C108 and R146,R149
because it's more easy to check.
Can you see the normal waveform?
YES
Check all power domain of LGE7329 (IC801)
(3.3V, 1.9V_CORE,1.26V)
& crystal output (X800 / 12MHz)&FRC_RESET
Measure Power & waveform at L800,L801,L802,L803,
L804,L806
because it's more easy to check.
Can you see the normal waveform?
YES
This board has big problem because FRC chip(LGE7329) have some troubles.
After checking thoroughly all path once again, You should decide to replace
LGE7329.
Although you replace it, you cannot see normal display, decide to replace
Main chip(LGE3159)
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Only for training and service purposes
NO
JK1201 may have problem. Replace this Jack.
NO
This board has big problem because Main chip(LGE3159) have some troubles.
After checking thoroughly all path once again, You should decide to replace LGE3159 or not.
Video
LGE Internal Use Only