I've got a 1959 Zenith C730 that I've re-capped, re-tubed and generally fussed over for about a year now. It's my favorite radio and I listen to it a lot, but it has a problem that I'm having trouble tracking down. At anything more than 1/4 volume, I get a buzzing, rattling sound out of the front that -at first- I thought was resonance that was causing the dial lens to buzz. I removed the lens and squeezed it back in with a few small strips of rubber (from an old bicycle tube) but the buzz remained. After that, I began tightening down every screw and nut I could find, including fussing with the plastic tweeter and the brace that runs from the chassis to the top of the cabinet. Still there. This radio has a deep tone that (I'm sure) is adding to the problem, but it's interfering with my listening enjoyment.
Perhaps it's the speaker itself? If so, any tips on where I can find one? It is roughly a 4x6 oval. I have other C730s (and G730s) but don't want to rip apart one good radio to fix another. Is there a vendor on the site that can help?