If you have a circuit which is normally designed to operate with an unregulated supply, through a regulator... say unregulated +8 through a 7805 to a regulated +5 and you want to test it independent of the +8 supply, if you leave the unregulated rail unattached and put +5 switcher straight onto the regulated +5 rail, will you damage the 7805? Clearly the VIN is open, but the ground pin will still be attached. Would this push voltage back through and screw things up? Thanks, Bill S.