David, your take-up problem is one of the two main issues that doom the 16CL (the other one being the rubber drive rollers turning to goo). It can be fixed. Remove the arm cover and you will see that one of the belt guide rollers is spring-mounted. Give a good clean to everything and check the tension. If you think that you can't get any more tension, you need to change the belt. Seller "isellprojectorbelts" on Ebay usually has some. It's the "smooth" or "early" version. You can also get the whole KIT
. Or maybe the spring is missing from the roller assay. The best solution, though, is to upgrade to a cog and toothed belt system. Very easy to change. LARRY URBANSKI
is a reliable source for the "ELMO 16mm 16-CL, TRV-16, REAR ARM UPGRADE KIT".
Before going any further with your sound problem, let's try the basics: Is your CL an optical or Opt/mag model? Is the exciter lamp lighting up ok? (sometimes, changing the lamp can fix a lot of things...) Can you check very carfefully if nothing is stuck in both the external speaker socket and the microphone input socket (at the back of the machine). Don't hesitate to remove the back cover (if you change your take-up system, you will have to, anyways.)
Keep us posted.