On Fri, 15 Feb 2008 22:01:48 -0800 (PST), you wrote: > >--- Cedric Chang wrote: > >> > >> > On Feb 15, 2008, at 7:38 AM, John Chung wrote: >> > >> > Guys, >> > >> > I have quite a few dead stuff thanks to faulty >> > transformers. Do anyone have any guides on >> repairing >> > transformers the practical way? One of the >> > main problems is that I do not know how much to >> wind >> > on the transformer..... The voltage values are not >> > printed on the transformer itself*can't work back Assuming you're talking about mains transformers.... The most common faults on transformers are internal thermal fuses going open - usually buried under a few layers of tape and easy to fix, and the wire fracturing where it connects to the tags/pins, also usually fixable, sometimes by cutting away part of the former to get to the end. The actual windings don't generally fail unless they have been over-run to the point of melting the insulation, and if this was caused in normal operation as opposed to another fault, you probably don't want to rewind with the same gauge wire as chances are it will eventually fail again. In most cases it should be possible to figure out the approximate output voltage by looking at things like capacitor voltage ratings,and replace the transformer with something similar. The VA rating can be judged from the physical size. Rewinding will very rarely be a sensible option - probably only worthwhile for an irreplaceable iece of kit with a muilti-wound transformer in a space that doesn't allow for replacement with off-the-shelf parts. Not sure if you can still get them but RS (rswww.com, not Radio Shack!) used to sell transformer kits with pre-wound primaries for winding custom transformers. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist