I just fried the mainboard on a Duo 2300c that I had almost compleatly restored.
Boohoo :^(
The good news is that I found the transistor that popped.
The bad news is that most of the casing is vapor.
The location of the part is DZ5, located about an inch from the bottom-back side of the board.
If anyone can read out this part number, I would be greatful.
The only letter I can see is an "???N"

Assume nothing, question everything. This is the path to true enlightenment, but don't take my word for it.