Zenith Cobramatic Stroboscope - Muffled Audio?

[Dubis7]

The audio sounds like it's coming through an AM radio. I bought this thing restored a few years ago, and the amplifier has previously been recapped and was working fine. Here's what I do know:

1: About a year ago, I damaged the needle while dusting it. Literally broke the thing off of the cartridge. I was able to source a new needle and install it, but for awhile I didn't use it because there was an issue with the drive mechanism that I fixed a few weeks ago.

2: Around the same time that I replaced the needle, I discovered that I had accidentally turned the turntable off but left the amplifier running. It may have been on and cooking the tubes for over a month at the time - is it possible that I wore out one or more of the tubes doing that? I just replaced the 12AU6 today but had no change.

3: I pulled a different, restored player out of the closet and tried this same record on it. The audio was much clearer, so this is definitely something up with the player.

Example video here: https://photos.google.com/share/AF1Q...d6SlJhQkJYVEZB