I'm no electrical engineer, but I did some poking with a friends voltmeter a while back, and if I remember right, I found the 5V before the filter but not after, and not in the appropriate pin on the ADB connector.

I found the Apple Guide to Macintosh Family Hardware at archive.org:

http://archive.org/details/apple-guide-macintosh-family-hardware

Here's the schematic for the SE and SE/30, which shows no fuse on the power line. The II, IIx, IIcx and IIci show a 1A fuse on the left side of the filter.