Vacuum cleaning is much more "dangerous" for a PCB than washing it. Pete made a very good point, one I had forgotten, the static charge

by dust moving through an insulated (plastic) pipe can generate some obscene voltages. Remember the old science experiment involving the comb generating static electricity? That voltage is enough to wipe nearly the entire board.

Remember the old science experiment involving the comb generating static electricity? That voltage is enough to wipe nearly the entire board. Like I said before, don't take my word for it. Take an old, dirty board that you know works, and run it through the dishwasher. Dot use the plate warmer or drying functions. At the end of the cycle, remove it, shake it off, and allow it to dry for several days (hang it up). Plug it back in - it'll work. And it'll look nearly new..... - Matt