Cobra tone arm wire

[Lincoln]

Can any shielded mono tone arm wire be used with the cobra radionic system, or does it require special wire.

I am also having trouble with the switch on the mechanism that switches back and forth from the upper and lower tone arm. Can this switch be eliminated so that both tone arms are always "on"?

Thanks
Lincoln

[Ron Rich]

Hi Lincoln,
As far as I know--wire, yes--
As for the cart switch--no.
Ron Rich

[Lincoln]

This is on a Wurlitzer 1250. I knew almost nothing about it when I got it. I have the mechanism restored to working order. Now I'm on the sound system. I have recapped the amp and replaced one bad tube. I have it playing but get lots of static and crackle. I've been reading about how the cobra system works and find it kinda interesting. Here is what I tried and found didn't work: since I only have one good cartridge I thought I would bypass the switch completely and hook the tone arm wire directly to the input wire to the amp. I got no sound doing this. I then hooked the switch back up, and used a clip to hold the contacts shut on the switch, I then got good sound. The only difference I can see when the switch is hooked up the terminal where the metal wire shielding is joined, is arranged so it is grounded through the switch mounting screws to the mechanism base. Is this the case, the shielding needs to be grounded for the cobra system to work?

Thanks,
Lincoln

[Ron Rich]

Hi Lincoln,
Since I don't have, nor want, a schematic for that 1250, I am guessing that a 'Cobra", like any cart., needs two wires connected. If the switch opens one side of a cart., I guess it should not work ? Ron Rich

[Lincoln]

Ron,

I don't blame you on not wanting a 1250 (schematic or machine). If you were closer I might leave it in your driveway and sneak away. This thing has changed my grey hair to white! I think I found my answer in one of my Dr. Know it all books, and am leaning toward it being a bad ground.

Lincoln

[Ron Rich]

Yes, one needs a good ground,and a good "hot" for mono audio ! I have been told by "older gents", that those double sided 24 play WurliTzers were "easy to fix", and "fix", and "fix again", and again, and again---- Ron Rich

[jukenorman]

I have seen it posted on another forum that the length and type of coaxial cable is important in a Cobra installation because the cable capacitance forms part of the resonant oscillator circuit. But it's not something I have experimented with.
Norman.

[Ron Rich]

Guyz,
I do believe Norman is correct ! I had forgotten about that fact when I spouted off before-- I apologize !
Ron Rich

[Lincoln]

I did notice that one of the European parts suppliers has a listing for Cobra tone arm wire. One size for the tone arm to the switch and one size for the switch to the amp.

Lincoln