This is the same set up used in KB and Baldor small DC SCR drives, if you are 'lucky' it is just the bridge components that are blown.
As you guessed, these are a bridge with 2 SCR's and 2 power diodes with one as a snubber.
If it does not appear that anything else is blown, you could just change out the power devices.
In one case, I fitted higher power devices on a separate heatsink.
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.