CFL autopsy.

The CFL in the kitchen is left on 24/7 - sometimes they last a very long time, this one not so much.

At first glance it looked as if the windings insulation on the feedback toroid had incinerated, on closer examination; a capacitor next to it had self destructed and sprayed its surroundings with ash.

The capacitor was on the negative end of the capacitive supply splitter in the half-bridge.

All the semiconductors tested OK, but the 2 transistors were heat discoloured.

The 4.7uF/400V electro read about half the rated capacitance and more than the 40 Ohm that the Atlas ESR70+ is calibrated to.

The mains in RFI filter inductor had sacrificed itself to save the fusible resistor.

The CFL was a Philips 18W.

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Ian Field
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