It seems to be an old Shindengen part number, and if so, it would make it a 3 amp, 250nS fast recovery diode. I would seriously suspect the capacitor it is feeding, I think it's C208 ( ? ) the large electrolytic that is connected to the diodes trace on the PCB. I bet that cap has developed high ESR or has become leaky, overloading the diode. Electrolytics tend to go bad after awhile, and it is common for them to destroy a feeding diode when they do.
Without an ESR meter, it would impossible to tell if the capacitor is bad or not. I would just replace it. For the diode, if you have access to either ECG or NTE replacement parts, it could be replaced with ECG or NTE #580 or regular parts such as a MR852 or a BYW95B
There appears to be some heat damage to the PCB, so check all the solder joints too.