Tsk tsk tsk! By the sound of it your Toshiba supply has incorrect polarity.
The marked component is a power diode that's there to protect against reverse polarity. Provided it wasn't destroyed completely there's a reasonable chance your receiver may still be OK.
I suggest you get a replacement DM500 supply (eg send Fernbay a PM, he has them for about $15). Give it a try. If you find the receiver no longer works then put it in the bin and buy a new receiver. Reverse voltage kills digital electronics devices very quickly.