Gen1 D2 light controller rebuild

how to rebuild Gen 1 dual intensity controller

The yellow wire going to each LED light is a PWM input, ~5V, 500 Hz and (at low beam) ~80% duty cycle.
Cobble up a simple PWM circuit using a NE555 IC. The NE555 can be biased so that the output goes to zero, resulting in full LED beam when the head light high beam trigger wire receives 12 volts. Solder up a little print that fits into the original case (Dig out the potted original PCB).
https://www.youtube.com/watch?v=i0SNb__dkYI
So with about $2 worth of parts and a couple of hours, customers can have Gen1 dual intensity controllers working again as intended.