Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uwm.edu!ogicse!milton!whit From: whit@milton.u.washington.edu (John Whitmore) Newsgroups: sci.electronics Subject: Re: step up transformer Message-ID: <15200@milton.u.washington.edu> Date: 26 Jan 91 02:21:33 GMT References: <1228@heurikon.heurikon.com> Organization: University of Washington, Seattle Lines: 28 In article <1228@heurikon.heurikon.com> johne@ex.heurikon.com (John Eckrich) writes: >map@zeppelin.rutgers.edu (O. C.) writes: > >>My brother and I are building guitar amps. Any help with inexpensive >>sources for step up transformers(120->350)? >Use a 40V (ie. 120 -> 40) transformer, and plug it in backwards. NO this is dangerous! A transformer has sufficient inductance to ensure that at its rated input voltage and frequency, current is limited so that the transformer iron does not reach its magnetization limit. Above this limiting current, the transformer is a short circuit. The 40-volt winding is lower inductance than the 120-volt winding, thus will proabbly saturate the transformer, and burn out your fuse (if you're lucky). There's lots of old vacuum tube equipment around that used moderate amounts of current at high voltage; for that matter, a microwave oven transformer goes from 120 to 1200 or so (some vacuum tubes are still around...). Look for an appropriate unit in a disused piece of equipment... somewhere. Parenthetically, 120/220V transformers for voltage conversion are relatively common; 220VAC rectifies to about 300VDC; would that do? John Whitmore