For future reference:
I had a bunch of new 4' T-8 florescent ballasts go bad. Different mfrs.
It might have been the damn Sylvania 'green eco' bulbs I used, or transformer spikes, or other.
I tried a bunch of those 'Plug-and-Play' 'Direct replacement' LED bulbs. Different mfrs.
None worked. They still use the juice from the ballast.
I started converting the fixtures to Ballast-Bypass LED. Marked the fixture so nobody else would use the wrong bulbs.
So much better now. Instant on. Full bright even in cold weather. No flicker.
And you can get different spectrum color tone bulbs.
It can be tricky.
Use the correct new small wire nuts and carefully wrap tight with tape starting from the wires.
Use logic, not necessarily the chart. Some bulbs use both sides.
If your cord isn't marked, split it and use a Non Contact Voltage Tester Pen to find the hot side.
https://www.rablighting.com/downloads/instructions/t8-ballast-bypass-single-ended.pdf