This shows the Zinsco main circuit breaker box and the thermal image of the bad breaker. According to a number of Youtube videos the Zinsco breakers and box are problematic and potential hazards.
One leg of the 240 volt supplied to the house is causing flickering lights--i.e. the 120 volt leg is intermittent. The lights went out for more than 5 minutes--allowing me to measure the voltage dropping to zero.
Here are pictures of the pedestal with the meter and connections to SDGE main power plug.
Replacing the circuit breaker in Zinsco box.
After replacing faulty circuit breaker lights flickered a little bit for first hour then stayed "solid on" after that hour. Thanks to Martin and Isaac for their work replacing the circuit breaker.