So I have an MR16 halogen light bulb like this one, 12V 75W, resistive (no LED). I have a 12V, 10A power supply. The bulb won't light. I figure the bulb requires 75/12 = 6.25A when running, though somewhat more when starting up (due to lower resistance when cool). Oddly, the cool resistance of the filament is measured to be about 24 ohms. I say oddly because the hot resistance should be 12/6.25 = 1.9 ohms, so the cold resistance should be even lower. At 24 ohms, the startup current should only be .5A, so the power supply should be adequate. Nevertheless, the supply comes on for about 40 msec., rises to about 8.3V, then shuts down and repeats every second or so (see scope pic below), looking like it's being overloaded. I've put a 6A load (as big as I have) on the power supply and it puts out 12V without skipping a beat. What fundamental principle of electronics am I missing today?