Re: No sound from TV tuner
You have to make sure that you have enabled the line-in for recording in volume control which is located under the options then properties area and also check that whether it is not muted or set to no volume at all. Apart from this, you will need a stereo audio cable to 3.5mm adapter which would go into the stereo headphone like a jack behind the card and also the 2 different stereo speaker connectors into the STB's audio out.
Re: No sound from TV tuner
Normally you must connect the card below the last PCI slot on the left bottom of the motherboard. First disconnect your tuner card, and you will find the sound on the HP. This card must be connected to the motherboard because the sound is an integrated chipset. Contact name and exact model of the motherboard to determine where it connects.