On Monday, October 29, 2018 at 6:53:34 AM UTC-7, Tim R wrote:
I had the ballast in an old two tube T12 fluorescent fixture go bad.

The local big box had direct replacement LED tubes on sale, so I tried them. They wire directly to line current, no external ballast, but the tubes fit in the old tombstone connectors.

Did you disconnect the ballast inside the fixture, that connects to those old tombstone
connectors?

They work fine; they start at full brightness even when the room is cold, unlike the old fluorescents they replaced. BUT there is a long delay between flipping the switch and seeing them start. It's on the order of 1 - 2 seconds, I haven't tried measuring yet.

Either the ballast inside the fixture has a start-cycle, OR there's some kind of switch-off
that operates to prevent a power surge from frying the LEDs. That protection circuit
can be triggered by the power-on transient, and take a while to reset itself.