i replaced all of it, but i did not use new ram.
that is the reaseon why apple logo still there.
every ram was tested on the another board using the slot.
(i mean 16 number of ram, not 16$
)Elfen //
thanks for your comment.
i also think about that. "adjusting voltage and brightness."
but when i connect another 128k logic board with machine, everything was fine.
so i guess the problem is not on the analog board.
and there is bong sound but very very soft (low).
i'm tracing the strange signal for using the osiloscope.
but i can't find the culprit at this time.
i will update as soon as possible.
thanks all.