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Old 10-27-2019, 08:44 PM   #1
klawockvet
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Default Radio Polarity Help Needed

My 47 came with a 6 volt Optima battery and a one wire alternator. It had and still has a negative ground. I have had the radio repaired and want to get it working but am unsure about hooking up to the negative ground. It seems I would have two options:
1. Reverse the polarity back to positive ground. Would that make any difference to the alternator? I know the ampmeter woud read backwards but I think everything else would be fine. Any comments?

2. Send the radio off to be modified to work on negative ground. I have heard this is possible but I'm not sure.
3. Do nothing and hope that the polarity is not going to be a problem. I dont want to do this unless someone with more knowlege has done it without a problem.
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Old 10-28-2019, 02:01 AM   #2
flatheadmurre
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Default Re: Radio Polarity Help Needed

The person repairing it would be able to tell you if it will work on neg. ground or not...it depends a lot on what was exhanged and if it has a solidstate vibrator in it now...
And alternators donīt polarize like a generator they have diodes in them that set if they are pos. or neg. ground...so donīt try and reverse it !
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Old 10-28-2019, 04:45 AM   #3
A bones
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Default Re: Radio Polarity Help Needed

Quote:
Originally Posted by klawockvet View Post
3. Do nothing and hope that the polarity is not going to be a problem. I don't want to do this unless someone with more knowledge has done it without a problem.
It is a problem! Do not just hook it up. Find an electronics tech man to help with converting to neg ground.

Or MacGyver a way to insulate the casing from grounding out. Use the power input for ground. Then supply power to the casing. Best tho is to get help from a pro, for a cleaner set up.

Good Luck

Just thinking I know radio repair guys are not as prevalent as they once were. But one area that still lives on is the truck CB shops. Asking in your friendly truck stop may get you what you need.
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Last edited by A bones; 10-28-2019 at 04:54 AM. Reason: more
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Old 10-28-2019, 08:23 AM   #4
5851a
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Default Re: Radio Polarity Help Needed

Tried to use early VW 6 volt in a Ford once. Insulated it real good and blew it when antenna cable got plugged in. Forgot antenna cable coax is hooked to the car body on the mast mount.
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Old 10-28-2019, 09:19 AM   #5
klawockvet
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Default Re: Radio Polarity Help Needed

I have tried to contact the person who repaired it but get no answer. I will have to locate someone new if possible. Thanks to everyone for the advice and tips.
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Old 10-28-2019, 09:50 AM   #6
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Default Re: Radio Polarity Help Needed

Didn't Henry have some threads on using a converter to power different voltage and polarity devices in his car?
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Old 10-28-2019, 09:56 AM   #7
philipswanson
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Default Re: Radio Polarity Help Needed

I used to have a '47 and changed the polarity of it. As I recall, there was one capacitor in it the needed to be switched around. Best to get a schematic and have a radio tech look it over. It is relatively simple.
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