I just looked at my "Guide to the macintosh family hardware: 2nd edition" and only the mac II line has the 1A fuse on the 5V section of the ADB line (because they have keyboard power on).

The SE and SE30 do have a 470 Ohm resister in series on 5V line on the ADB data line (PIN 1 on the connector) you might want to look at.

The ADB signal is described as: Bidirectional data bus used for input and output. It is an open collector signal pulled up to +5 V through a 470 Ohm resister on the computers main logic board.