Check you did not pull up traces or thru holes on the sound board. Meter out the traces on the board and make sure. Add jumpers if necessary.
The large cap replacement should be a last resort on these boards as traces and holes are VERY easy to damage.
Some other possible causes of crackling sound are: speakers, the voltage regulator is going or tantalum cap/s going/gone or possibly amp chip heating up due to drying out heat transfer paste or loose heat sink.
Break out the DMM and good luck!
