If no background noise whatsoever is heard when your ear is placed close to the speaker then the first thing that any engineer would be doing is to establish if any of the two connections to the speaker has fallen off, and if not then take measures to check the continuity of the actual speaker coil. If you do not possess a test meter with an ohms range used for this purpose, then with the aid of a couple of wires connected to a small 1.5volt battery, quickly touch (scrape) them across the speaker connections, this resulting in a plopping noise through the speaker if everything is OK. These are obviously extremely basic measures, and if it isn't the speaker then proper fault finding procedures with the aid of a test meter will be required. PS: another long-shot, if this set has a headphone socket check if audio is OK in the headphones, and if so then rapidly plug the phone jack in and out a few times as it would indicate that the switchover contacts are faulty. (Oxidised)