The problem is likely an open circuit protector (pcb fuse) in the charging circuit on the board, particularly if the laptop had a dodgy battery causing heating. Another possibility is that the dodgy charging socket centre pin has burnt an internal pcb layer connection, this used to happen with amazing regularlity with Packard Bell's in particular, but also on Tosh on occasion. Or as has already been mentioned, the socket is shorted or a solder splash has been placed on the board accidentally. It's also a possibility that you have a short on the mainboard, but I think that's remote.
Look for the simple things first, check that you have your power rails up when the charger is plugged in, if not trace from the power source (socket) until it disappears. If all apears ok and no components have failed, then remove the RAM, Hard Disk, DVD, Processor and Screen and try again, if the rails come up, then refit each module one at a time to eliminate the faulty components. Methodology is the key to good fault finding. Make notes of your results so that you can refer back to them if you need to change your approach.
rgds