On Fri, 6 Jan 2012 05:55:10 +1000 cdb wrote: > At work I repair some ballasts that use 2 * TIP41's, these die on a=20 > regular basis often burning a nice hole in the PCB at the same time as=20 > disintegrating. Is the circuit with the TIPs a very simple one - say just one toroid and an air-coil or so? I had several burns using such a circuit. I am not really certain about the failure mode of these ballasts, but I suspect they hold a grudge against bad contacts to the tube pins. The circuit has no protection at all built-in. I gave up, tore the board out and replaced it with a more modern one. (Just for info, these use MJE13007 transistors). The ballasts are less than 10 dollars, much less than sitting down and repairing costs. John --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .