Have you seen this AFM Strobe troubleshooting site:
http://www.iobium.com/fixing_the_afm_strobe_board.htm
Guide to the AFM Strobe Board
http://www.home.earthlink.net/~zeecarr2/STROBE.pdf
Troubleshooting Process
http://www.home.earthlink.net/~zeecarr2/AFM.doc