mccormack tlc-1 front panel knobs slipping

First, pull the knobs off the preamp. Then take a small pieces of paper (about the size of a gum wrapper), and wrap them over the ends of the shafts and push the knobs back on. The paper allows for a much tighter fit. You may have to experiment a little with different thickness of paper depending on how loose the knobs are. You'll be surprised at how well this fix works.

Good fix that should work fine. If u want to know the screw size just contact SMcAudio and you'll get a quick and helpful rely.

An alternative to the method recommended by Zd542 is to wrap the shafts with plumbers teflon tape. Keep adding wraps of the tape until the knobs fit tightly. The teflon tape has no adhesive so it's easy to adjust or remove if needed.

This trick also works well with IEC power plugs that don't fit snugly into the socket.