Originally posted by mr.clean
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I agree with what you're saying.
I take it that the rectified output from L2 is whats lighting the bulb.
So should be easy to check the current & voltage with a dc meter to get how many watts of power the bulb is consuming.
Then measure the ac voltage & current from the variac to get the input power that's being used. Then you can compare the two wattages to get your answer.
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