1948 Magnavox "Berkley" Console Issues

[Electronic M]

The original Zenith cobramatic changers did NOT have turnover cartridges. The first year models 1948 were 78 RPM only, and later models that had 33RPM had a single stylus that was a compromise tip size part way between LP and 78. The Zenith designed cobra pickup was originally a variable capacitance cartridge that FM modulated an oscillator tube that was demodulator for audio. None of these cartridges supported multiple styli. Zenith kept this scheme until the mid to late 50s then they switched to generic third-party ceramic turnover cartridges, but perplexingly kept using the cobramatic name and tone arm design for a while after the switch.

[vortalexfan]

Originally Posted by Electronic M

The original Zenith cobramatic changers did NOT have turnover cartridges. The first year models 1948 were 78 RPM only, and later models that had 33RPM had a single stylus that was a compromise tip size part way between LP and 78. The Zenith designed cobra pickup was originally a variable capacitance cartridge that FM modulated an oscillator tube that was demodulator for audio. None of these cartridges supported multiple styli. Zenith kept this scheme until the mid to late 50s then they switched to generic third-party ceramic turnover cartridges, but perplexingly kept using the cobramatic name and tone arm design for a while after the switch.

OK, my bad, I was thinking that because I have an old Zenith S-9011 Record Player from the early 1950s that has a two tip needle arrangement that you have to "flip" the needle (its actually more of a cantilever) by pressing the back of the tone arm which allows the needle to switch between an LP or 78 Needle, and that record player is called a "Cobra-Matic".

Anyways that doesn't answer my question as to why the original factory phono input hookup on the back of this radio is not responding to any "electrical signals" being injected into the audio cable but will respond to "electrical signals" being injected directly into the phono input itself minus the audio cables.

[nasadowsk]

Originally Posted by Electronic M

The original Zenith cobramatic changers did NOT have turnover cartridges. The first year models 1948 were 78 RPM only, and later models that had 33RPM had a single stylus that was a compromise tip size part way between LP and 78. The Zenith designed cobra pickup was originally a variable capacitance cartridge that FM modulated an oscillator tube that was demodulator for audio. None of these cartridges supported multiple styli. Zenith kept this scheme until the mid to late 50s then they switched to generic third-party ceramic turnover cartridges, but perplexingly kept using the cobramatic name and tone arm design for a while after the switch.

Wurlitzer used cobras for a few years. Far longer than they should have. Seeburg and AMI had far far better sound systems that blew the Cobra out of the water. Wurlitzer finally dimped cobra when stereo came around…

[vortalexfan]

I got it fixed, it was a short in the wiring from the tonearm to the amplifier, apparently the way I had it wired up was that the "ground lead" of the headwire was tied to the chassis of the turntable which was causing a short, so I wired it so that the ground was floating separate from the turntable chassis and now its working fine.

Unfortunately the cartridge (a Sonotone 2T) is nearly dead because its not putting out much audio (the volume has to be cranked up to the halfway point to even hear anything) which means I'm going to have to find another mono (Hi-Fi) 1/2" mount flip-over cartridge to use with this record player.

Any suggestions as to a good replacement cartridge to use with this record player?

[vortalexfan]

Update: I picked up on the cheap (I was the only bidder) on feebay a lot of 30 record player serviceman items (including several cartridges, needles, a needle tracking weight scale, tonearm wire, cartridge mounting screws and spacers, a desoldering bulb etc.) for $9.99 plus shipping and one of the cartridges in the lot happened to be a NOS Sonotone 2T Cartridge so I should be good to go to get this unit fixed up the rest of the way!

[vortalexfan]

OK so I have a quick question, this radio uses 2 6L6Gs in push-pull configuration for about 45 watts or so and when I got this unit it had its original matched set of Ken-Rad 6L6G tubes in it but one of the tubes was microphonic and I happened to have a Conn Rebadged GE 6L6GC tube that I salvaged from an old Conn Organ Amplifier to sub in to confirm my suspicions about one of the original 6L6G tubes being microphonic.

I know with push-pull amplifiers it is best to replace tubes in pairs but unfortunately 6L6G tubes (NOS) are $40 a pop and 6L6GC tubes are $80 a pop, and I have a whole ton of 6V6 tubes laying around including a matched set of Zenith (Sylvania) 6V6G tubes that I salvaged from a Zenith 10S690 Console that I parted out.

I was wondering if I could use those 6V6G tubes in this Magnavox Console in place of the 6L6G tubes since the 6V6 tubes are more readily available and cheaper than the 6L6 tubes?