How to repair lg crt tv bottom darker.

LG TV 21''NORMAL PCB
MAIN IC TDA9340PS/N3/A/1833
FBT 6174V-6006E/6002K
VERTICAL IC TDA4863AJ
SOUND IC TDA7297
AV IC TDA9859
STR W6754

PROBLEM: BOTTOM DARKER/LESS

SOLUTION:
1.Power on/Check vertical section.
2.Check vertical supply positive voltage----------ok.
3.Check vertical supply negetive voltage---------ok.
4.Check vertical ic TDA4863 all pin voltage------overall ok.
5.Check main ic (pin-21) vertical feedback(Vb) voltage----low.
6.Check main ic (pin-22) vertical amplify(Va) voltage------low.
7.Check main ic (pin-25)Iref. voltage-------ok.
8.Power off/Measure registor R504(39K)-------high registivity.
9.Open the registorR504(39K).
10.Again check the registor by meter------high registivity.
11.Set new registor 39K.
12.Then------------