i have a suitable heatsink, well, it worked well for my dry cell circuit anyway (salvaged from a nikko remote control car). I thought that it was the out put, and i replaced the 4ohm speaker with a 8ohm speaker. But the same happened. I dont see why it could be a circuit fault, as it worked for the dry cell circuit, but i rebuilt the circuit again with new parts, but again, the same happened. I will start from scrtach again as soon as i order another few of the chips.