Adriatic posted:The delay makes me wonder about a bad capacitor or resistor leading to one. Look for swelling etc. on caps, or dark resistor. Can you check voltages? Diodes? Maybe you've lost a leg off rectification.
When does the light come on? Ever?
The headlight comes on at the same time as the engine begins to move (in reverse).
Here are some photos of the board. (Note that the original K-Line board was replaced with a Lionel board (691-DREU-A) many years ago, and the engine has run fine until now. Also, please excuse my lousy photography.)
My untrained eye doesn't see anything externally wrong with the components on the board. Note the capacitor under the board; it also looks OK to my untrained eye.