Faint sound is almost always the SMT electrolytics on the motherboard, those things are horrible. I would replace the ones in the tuner as well, there is a good chance that replacing ALL of the SMT lytics with tantalum or ceramic capacitors will resolve all of your problems.
I've also found that the large through-hole electrolytics rarely fail, only those that are in the output filters of the power supply. The big ones I only replace if they test marginal or bad, the smaller ones in the power supply and any surface mount electrolytics get replaced wholesale. It's not even worth troubleshooting until you do that.