My favorites (on-topic as they are OLD!):
Probe - Issac Asimov does Columbo. Cheesy, but mostly hard sci-fi storylines
(AI, ball lightning, etc...)
Riptide - Another detective show - kinda like the Rockford Files mixed with
Wargames. Even cheesier than Probe, but more fun to watch.
Stingray - Yet another P.I. show with a some science-based puzzles. The one
that sticks in my memory was a biosphere type operation where people were
going mad and killing each other. Turned out it was overheating electrical
conduit that roasted PVC piping, that leaked toxic vapor into an HVAC vent.
This show was *really* well shot.
The Secret Life of Machines - A stuffy professor builds cool gadgets to show
how everyday machines work. One of the best shows ever about engineering.
Mr. Wizard - I caught the 80's incarnation on Nickelodeon. I lusted after
his Vectrex and Heathkit Hero...
Junkyard Wars - More recent - teams pick through a junkyard to build
machines that compete against each other. My favorite - an antique Rover
turned into an amphibious car. They simply cut the rear drive axle and
bolted a propeller to it. Brilliant! I miss this show...