Alex Trebek dug deep into his pockets again to help a homeless shelter get a new facility off the ground -- more than doubling his previous donation for a very similar cause.
Ken Craft-- founder of Hope of the Valley Rescue Mission -- tells TMZ ... Alex handed over $500k of his own money to help Hope of the Valley with a brand new homeless shelter they're aiming to get built over the next year or so in the San Fernando Valley.
This new initiative is mega -- they're calling it Hope Central -- and we're told it'll be a 50,000-square-foot facility that'll house homeless seniors in the area. The team is currently scouting properties and will break ground in 2021 -- now, with much more ease thanks to Alex.