820-01598 water damage

Came in heavily corroded. I ultrasonic cleaned and reaplced both bad CD3217 and now computer is turning on. everything is working execpt there is no sound. sound is being detected in system prefs but sound is coming out of speakers. i found a couple of shorts around u6400 so i removed it and shorts went away. replaced it and all is good, but still not getting sound. the only issue is a short to ground on spkramp_rl_mode. i replaced u6400 again and replaced r6481 but still same issue. if i remove the resistor the short to ground goes away. i am at a loss on this. did i get 2 bad chips? is this suppose to show short to ground?. i don't think so becuase spkramp_fl_mode is not on u6450 side.
 

2informaticos

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R6481 is 0 ohm resistor, CONNECTED to ground; what value did you expect to get there?

Corrosion under (or around) U6400/50 is very dangerous; several T2 lines are connected there.
Leakage from PPBUS_G3H damaged T2.
 
Just trying to understand here. if t2 was damaged wouldn't that stop the laptop from powering on? and second question. Since c6406 was short to ground (PPBUS_G3H_SPKRAMP_LEFT) wouldn't that have stopped power from going to t2?
 

2informaticos

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T2 is a complex chip; it may get partial damage only.
One time I got 01521 with SPKRAMP_RESET_L shorted to ground because of liquid spill on audio board.
Machine had even heaphones sound, but nothing on internal speakers.

There was sufficient time for leakage to T2 lines, before C6406 shorted PPBUS_G3H...
 

2informaticos

Administrator
Staff member
I don't see other reason, as you found corrosion there.

Some lines may have test points, or external components connected.
Other lines can only be accessed under audio amps.
However, is wasting time to remove the chips; the problem is clear...
 
just for an update on this case. i ordered a donor board and dioded tested all the pads comparing to the working board. found a reading that was off and found a resistor that was not to spec. replaced it along both chips and now have speakers. moral of the story is test all the lines :)
 
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