Philco 38-7CS restoration

[bandersen]

The wooden knob has a brass/bronze bushing. The plastic one doesn't.

The conecentric tuning is a weird mechanism. The original knob would have been bakelite with a spring behind it. You push it down hard so it rides against the knurled ring around the dial face then you rotate it. That's the 'fine-tuning' So the knob both slides up and down and rotates on that brass shaft.

I bet the original knob wore out from use and they substituted the wooden one. I've tried this knob briefly and while it looks great it seems like the plastic rubbing on metal won't hold up.

This video shows how it works: http://www.youtube.com/watch?v=_VIknHBh3J0