Posted by RUSS (member) on January 10, 2001 at 11:53:00:
I saw some discussion a few days ago regarding Vinny's 6 volt/12 volt conversion. I'm coverting my 6 volt postive ground system to a 12 volt negative ground. I just, last Xmas, spent $250.00 having my radio restored. Is there a way to use my 6v. negative ground radio on the 12v postive ground conversion or am I going to have to spend another $500 to get it converted to 12v?
I would appreciate hearing other options.

Posted by LARRY JORDAN[member] on January 10, 2001 at 21:12:30:
It makes no difference to the radio if your battery is pos. or neg. gr. Just get one of those voltage reducers that looks like a round piece of white ceramic with the curly spring and two screws. Put it in your current supply line. One is all you need. I have mine mounted under the hood, on the driver's side fender well, toward the firewall, in that section down low where nothing will get to it. It's been like that for a couple of years and works fine. Larry

Posted by Keith on January 10, 2001 at 21:41:50:
In Reply to: Re: 6 volt Radio/12 volt system posted by LARRY JORDAN[member] on January 10, 2001 at 21:12:30:
Larry are you saying that you have an original 49-51 Ford radio and you reversed the polarity and it still works OK? I understand dropping the voltage.

Posted by LARRY JORDAN [member] on January 13, 2001 at 22:41:29:
In Reply to: Let me get this straight posted by Keith on January 10, 2001 at 21:41:50:
Hello Keith; I do have a stock radio. It makes no difference if your radio is pos. gr. or neg. gr. As long as the wire that feeds the radio through the fuse is a live one, carrying 6-8 volts or so that's all you need. The only thing that needs to know if it's pos. or neg. is the battery, reg, and generator [or alternator]. The starter does not have to be changed either. It will work pos. or neg. and 6v. or 12v. Thanks, Larry.

Posted by Sam on January 10, 2001 at 21:57:08:
In Reply to: Let me get this straight posted by Keith on January 10, 2001 at 21:41:50:
Larry are you saying that you have an original 49-51 Ford radio and you reversed the polarity and it still works OK? I understand dropping the voltage.

It is my understanding that all can be covered by changing the existing vibrator to a negative ground. This was told to me by the guy who rebuild my radio. Haven't tried it yet...

Posted by Gene(not to be confused with gene) on January 11, 2001 at 07:28:08:
In Reply to: Re: Let me get this straight posted by Sam on January 10, 2001 at 21:57:08:
The vibrator doesn't know about polarity of the system, accept for which direction it first starts to vibrate in, which is invisible. And, except for the tube heater elements, the rest of the radio depends on what comes out of the vibrator/step-up transformer circuit.
Different radios (6,7 or 8 tubes) draw different amperages, but your basic 1-ohm, 100 watt wirewound resistor will be close enough. Once the resistor is inline, the radio doesn't know the system is 12-volt, positive or negative. Just be sure to mount the dropping resistor somewhere where it won't be accidentally short-circuited, and where its surroundings can stand to feel a little heat (like that of a 40-watt light bulb).
If one knew his way around inside the radio, pairs of tube heater elements could be wired in series to split the 12-volts, and a small dropping resistor could be installed in the vibrator/step-up transformer circuit.

Posted by Keith on January 14, 2001 at 10:37:51:
In Reply to: Re: Let me get this straight posted by LARRY JORDAN [member] on January 13, 2001 at 22:41:29:
Larry, I had never even thought about whether you could change the polarity of a 50 Ford radio and it would still work OK, After looking over the schematic I don't see any reason why it wouldn't work. In regard to the starter button and the solenoid. I can see no reason why the button wouldn't be OK but I am not sure about the solenoid as I recall the direction of current flow determines which way the core moves. For somene who has a hard time remembering what happened yesterday, it is a little bit risky to try and remember what I learned almost 50 years ago.

Posted by 286merc on January 14, 2001 at 11:23:35:
In Reply to: 6 volt Radio/12 volt system posted by RUSS (Member, if Tim ever cashes the check) on January 10, 2001 at 11:53:00:
Hi There, you didnt mention the year but here is a general procedure.
Replace the 6V tubes and lamps with 12V equivalents. Use a 12A6 for the 6V6 or if you have the deluxe radio, wire the pair of 6V6's in series if you want. The 12A6 is available as WW2 surplus. Replace the vibrator with a 12V version or go solid state. Similar procedure for most radios using octal, loctal or miniature based tubes.
You can get most of the parts from Antique Electronics Supply in Tempe, Az. I'm against using a series dropping resistor since the initial surge will put lots of stress on the tube filaments and the transformer windings.
A more elegant solution is to construct an external SS regulator that allows ALL original electrical stuff to remain original, just the starter goes to 12V.
Carl
Rebuilding auto radios for 40+ years

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