I have no idea what the old firmware was. And no, I didn't back it up. My searching revealed (erroneously?) that the DW-Q28A is the same as the DRU-800A which is the same as a LiteOn SOHW-1693S. So, anywayI think I got the firmward from the rpc guys.
However, when I tried flashng something not specifically for the DW-Q28A, I kept getting error messages.
Still scratching head.