Hello all, I've been working on a 28v 3a power supply for an old computer I have, but I've hit a standstill with my circuit. I have a transformer with 24v 4a secondaries, which is rectified with an 8a standard bridge and 3300uf worth of filter caps. This brings the clean DC up to about 34v. All working well. Next I have a basic lm317 circuit with a pot to select between 4 and 30v, also working, I can plug a 12v fan or bulb in at the appropriate pot settings with no problems. To boost the current to 3a I have a 2n3055 pass transistor mounted on a heatsink, with the base pin tied to the 317's output and the collector tied to 34v DC. When I put my computer fan on the emitter to test, it 'jitters' back and forth, as the voltage is spiking all over the place (between 12 and 0). All power everywhere else seems good, don't understand. It worked for a few mins when I first build it then after recycling it did the same. I've gone through two transistors now... Does anyone have any ideas? It is modeled around dozens of like circuits online, makes no sense.
Thanks!
(sorry if this is the wrong forum)
Thanks!
(sorry if this is the wrong forum)
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