You can hear it for a moment when you turn it off? If so that sounds like old cap goop causing a short somewhere. Remove the op amp nearest the AV jack, Clean really well, and then re solder the op amp back. Lots of times old cap goop gets under there and shorts things out. If that doesn't fix it then check under the other two 4558 op amps. If that checks okay then start double checking the traces to all the caps you changed. Sometimes old cap goop gets in the via holes and creates issues.