re: I need help to identify a component on speed control circuit board

Klaus is 100 % correct.
Now have you isolated the fault to this component?

If not very carefully remove the board and turn it on there should be mains voltage diagonally across the bridge with the tilda marks (AC symbol) ~ then DC mains on the other two diagonal pins ( + and – )

Bridge rectifiers usually show some sign of fusing when failing, so there may be a small crack in the case or epoxy somewhere.

There should also be a part number on it somewhere (or possibly a coded number) as well but from the looks of it its a possibly a 5A rating or thereabouts.

What are the details of the Drum Sander please?