Hi Shaun. Over here in Oz we go through a lot of transformers in fence chargers. And quite often your "transistor" is an SCR. I suppose that you used a suitable replacement for whatever it has? The transformers have a tendency to arc over inside which may take up the transistor/scr. If you know what the dc voltage powering the primary is, you may be able to substitute (just for a test) a mains power transformer - For example if the rail is 12V you could try a 220:12v power transformer, connecting the 12v winding instead of the primary of the original. If it then keeps ticking over without destroying the semiconductor, maybe you need a new transformer. The manufacturers over this way (a lot of the chargers are made in New Zealand) refuse to hand out schematics. But it's fun to draw it out yourself, though it is probably a waste of time. Transformers over here are quite expensive, I have rewound one or two, but the complete outfits are cheaper now so it doesn't happen much any more. A farmer friend replaces the HV transformer with an ignition coil from a MV but don't try it if the outfit runs off the mains as in that kind of charger usually the HV fence transformer is the only isolation between mains and fence, and the ignition coil wouldn't come up to specs in the safety dept.. (LETHAL !)
