In response to the recent "PSU problem" thread... Yes, it is possible to build a bipolar PS from an untapped AC transformer: http://s1115.photobucket.com/user/MacDoktor/media/SDIY/Untapped-bipolar-PS_zpsb5a3a881.png.html This is the third time I've posted this since 1997. 8) Terry Bowman, KA4HJH "The Mac Doctor"