Apple quadra.lc 630.performa 640 Service Manual

 

 Troubleshooting

Symptom Charts/Audio - 4

 

Crackling noise is 

present when you 

play sounds other 

than system beeps 

and you are not in 

“play through” mode

1 If static noise varies when you adjust volume by Sound 

control panel, use  Audio Volume Extension 1.1 or later.  

Note:  Audio Volume Extension is available from standard 

Apple software update sites.

2 Replace logic board.

This applies to DOS-

compatible 

computers only: 

Static through 

speaker with optional 

sound adapter board 

installed and Internal 

CD and Playthrough 

option selected.

Replace the sound card, PN 661-0253.