Online resources for Electronic training? - Its apparent I need a refresher.

Long ago I worked as an assembler for a medical electronics company.
(70's)

My reference books are 70's era too, half full of tube circuits...

In the early 80's I moved to the metals trade, becoming a certified
occupational weldor in SMAW, MIG, TIG, Flux-core, submerged arc, and
Oxy-Acetylene. I worked my way thru college as a production weldor
while adding machinist training and finally adding CNC operations and
programming.

I have not worried the details of electrical circuits since.

Now I'm looking at (toying with) a bunch of simple circuits as part
of a few CNC builds or retrofits. I have little trouble following an
existing schematic, but I find myself drawing a blank when my needs
require modifications of the basic circuit.

I guess I need to go back to square one and take a full refresher. I
have forgotton soo much yet other areas are soo clear - (getting old
I guess.) I'm looking for something that starts out at beginer level
and works up. Ideally online where I can work thru it at my own pace
and as budget allows.

Ideas?