Zenith Cobramatic Stroboscope - Muffled Audio?

[Electronic M]

Haven't seen a photo to know if this was one of the capacitive REAL cobra pickups, but if it is a normal audio signal from a normal audio source won't work.

The early cobras used a variable capacitance cartridge that NOBODY else made (and only wurlitzer bought from Zenith to use). The capacitance carts needed a tube RF osc that was modulated by the cartridge to make sound out of the variable capacitance. Zenith used this from 1948 until the late 50s when instead of making a stereo version they just used the stylized cobra tone arm with a conventional ceramic or magnetic cart.

[Dubis7]

I'm not sure what mine started off with, but I know that the cartridge was replaced with a modern, stereo compatible equivalent. It's not the radionic cartridge so I presume mine started its life with the ceramic cartridge.

Unless I'm mistaken and the radionic could have been replaced with a modern cart without significantly redesigning the electronics.

[Dubis7]

Just for sake of an update, I think I have a plan worked out. It's a bit convoluted so bear with me.

I've been wrapping up a restoration project on a Norelco EL3542. Thing's basically done, I'm just seeing if I can quiet down the takeup reel clutch before I haul it back up to my office.

A few days ago, I picked up a Wollensak T-1500. Unrestored, but it came with an adapter cable that allows a 1/4" audio jack to connect to an external source using alligator clips.

So - knowing that the Norelco is tested and sounds great, and with that cable in hand, I should be able to comfortable check the speaker on the Zenith and then work my way back to the amplifier to see if I can narrow down the source to a speaker or amp issue. Worst case, if it's the amp I can crack that open and see about sorting out the issue.