Your tuner should have detents. IIRC around then RCA was using a ball bearing and spring to make a detent and if the ball falls out you loose detent.
A DTV converter box alone won't work. You can use an HDMI to ATSC modulator if you want (it's expensive, but has it's advantages). In this video I discuss doing just that in my set up.
https://m.youtube.com/watch?v=hKjt3x4WtWU
An HDMI* or VGA to composite video converter and RF modulator is cheaper and will also work. * DVI, Display Port, and HDMI use the same basic electrical interface so you can buy a cheap dumb DVI to HDMI or display port to HDMI cable if your computer doesn't have HDMI output.