The earliest '817's had no fuses, but got a 3.15A battery fuse (F1001) for the second revision.
ND's got a second 2.3A "protector", F1002, for the 13V lines going down to the PA board.
This might also prevent destruction of the PA transistors when it goes unstable.
F1002 in my ND has gone in the past.
I would probably add it if I had an '817 I was fixing.
