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To Main MENU Here are some messages covering radios. I have included the e-mail addresses if you wish to reply directly to the original poster. I will add more from time to time. I am always looking for volunteers to help compile and maintain these FAQ's. If you are interested, E-Mail me. |
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This is a very popular subject. Especially converting from positive to negative ground.
Date: Wed, 26 Feb 1997 10:29:56 -1000 (HST) From: Tony Clarke tclarke@soest.hawaii.edu To: xke-lovers@listserv.azstarnet.com Subject: Ser 1 radio polarity Hello out there in radioland; I just re-discovered in my Jag stuff an early sixties Radiomobile (made in England) radio that appears to work and looks to be correct for my 64 XKE OTS. However, it is positive ground and my car has been converted to negative ground. Does anyone know if there is a way to convert the radio to negative ground? [It has an sticker saying for positive ground only]. It is also missing the chrome (I think) face bezel. Does anyone have one or know where to get one. Thanks
Date: Wed, 26 Feb 1997 18:28:28 -0800 From: George Cohn gwcohn@mindspring.com To: xke-lovers@listserv.azstarnet.com Subject: Re: Ser 1 radio polarity Tony Clarke wrote: > > Hello out there in radioland; > > I just re-discovered in my Jag stuff an early sixties RadiomobileWhen I had my original '64 OTS, I bought a convertor to convert 12V positive ground to negative ground so I could install a nifty Motorola 8-track player (remember 8-tracks?). I'm not sure, but I think I've seen a convertor that also does the reverse. I would start by checking in the services section of Hemmings. I believe I've seen ads in there for companies that convert electronics from one polarity to the other.
A note of warning: I used to work in a radio-TV shop as a kid. Most
early car radios have a million grounds that all have to be changed to
reverse the polarity. You would probably be a lot happier with the results if
you can find a negative to positive convertor rather than try to rewire the radio.
Date: Wed, 26 Feb 1997 18:17:04 -1000 (HST) From: Tony Clarke tclarke@soest.hawaii.edu Subject: Re: Ser 1 radio polarity Thanks George and Steve; I guess I have the later one with AM/FM/SW. I guess I am also puzzled about this converter. If the Radio is grounded to the panel and if it is a negative ground car the radio chassis and guts will be at negative ground. So how can this converter work? I have made a radio work before on reverse polarity by isolating it from ground of the car (use wood panels and nylon screws to mount it) and keeping the input polarity the same as original. Of course if you short the radio chassis to car ground then it is fireworks time - a situation that is not desirable in a 30K car. Tony On Wed, 26 Feb 1997, Steve Kemp wrote: > I've seen others purchase the converters, so they probably > still exist. On, the radiomobile (AM) radio I have, the > escutcheon was brushed aluminum. The later ones (am/fm/sw) > are much fancier and chrome. > > SK > 62 OTS Date: Wed, 26 Feb 1997 23:45:38 -0500 (EST) To: xke-lovers@listserv.azstarnet.com From: Larry Schear twincam@voicenet.com Subject: Re: Ser 1 radio polarity Tony - It's probably easier to convert the car back to positive ground! If the radio's circuit boards are all floating and are not tied to the chassis for more than mechanical support, you (or a knowledgeable individual) might be able to rewire it so as to operate as a negative-ground radio. Mountings, ferrules, filters, electrolytics, connectors, all have to be modifiable. An alternate suggestion would be to 'gut' it and install the works from a negative-ground radio in the shell, then install normally. If you install the unmodified radio in such a manner that it is electrically isolated from the car's chassis (mount in plastic frame, rails, nylon bolts, etc.) and you succeed in floating the shield of the antenna and feed line in a similar manner, then someone will inevitably brush against its metal bezel or knobs at just the wrong time, with a pencil, bracelet, or whatever, causing a flash, burn marks, and loud screaming! If you's like, I'll look at the radio for you and tell you what I think about converting it; a good auto radio shop (do they still have those things, or did they go out with vibrator power supplies??!!) or electronics repair center could also provide said service. Good luck!
Larry Schear
From: radiowsh@mindport.net radiowsh@mindport.net To: xke-lovers@listserv.azstarnet.com Subject: Re: Ser 1 radio polarity Date: Thu, 27 Feb 1997 13:22:33 GMT The easiest way, by far, to operate a positive ground radio in a negative ground car (or vice versa) is to obtain a polarity inverter. This will change the polarity of the applied voltage to the radio, and does not require any alterations of the radio itself. It is a small box that hides away under the dash. The connections are few and simple. Our source for these devices is Antique Automobile Radio, Inc., Palm Harbor, Fla. (800) 933-4926. (Standard disclaimers apply) These devices have limitations, however. They may not be used to power devices that draw current in excess of their ratings. A standard inverter is capable of providing a little over 2 amperes while heavy-duty units can provide nearly 5 amps. In most cases, this would require that the radio be solid-state, not tube-type. While some dual-polarity radios were made, one should avoid the temptation to try to internally rewire a single-polarity radio to its opposite gender. We've seen the results of such attempts in which perfectly good, often rare radios, are destroyed. The cost of undoing these experiments can turn your hair gray. Many of our clients look for dual-polarity Motorola radios of that vintage. The radios are correct for US spec cars, convenient to install, and, very importantly, small enough to fit in the E-type console without interfering with the speakers. It may be worth the wait to get such an radio.
Vince Chrzanowski
Date: Thu, 27 Feb 1997 05:54:48 -0800 From: George Cohn gwcohn@mindspring.com Subject: Re: Ser 1 radio polarity The convertor actually is a power supply that converts the incoming DC to AC, then it is rectified and converted back to DC. Because there is a transformer in the AC portion, the input and output sides are totally isolated from each other. Therefore you can ground whichever side is needed at the output.
Simplistic explanation but I hope you get the concept.
From: Rod Polentz RodPolentz@aol.com Date: Fri, 28 Feb 1997 12:09:15 -0500 (EST) Subject: Ser 1 radio polarity I have an alternative suggestion. Those 30 year old radios don't sound too good, never did. So, if your car is concours why don't you just put the pos. grd. radio in the dash and call it good. I have never seen a concours judge ask an owner to turn on the radio to see if it worked. And, if your car is not concours, why don't you put the old radio on the shelf and put in a modern radio with cassette, etc. Or, I guess you could put the old radio in the dash and wire a modern radio in a remote location so you can listen to decent quality sound? That's just my two cents worth.
From: Imk1968@aol.com Date: Fri, 28 Feb 1997 17:35:39 -0500 (EST) Subject: Re: Ser 1 radio polarity I installed an inverter. I purchased it from J.C. Whitney in Chicago. Allows me to use radio / radar detector / cell phone on my 64 E-Type Cost was about 60 bucks! Allows car body to becommon ground to both positive and negative circuits. Works great and there is no line noise. Best of luck! Date: Fri, 28 Feb 1997 22:11:29 -0800 From: Steve Kemp Subject: Re: Ser 1 radio polarity This is near identical to what I used to do in my last concours car. The radio and equalizer/amp and rear speakers were mounted in a long box that rode on the back bulkhead. A small jack and cord was extended under the seat to derive power and actually disconnect and reconnect the front speakers in the console (for four speaker sound). A bypass plug was inserted when I showed the car so that the console speakers actually worked with the regular radio.
SK
RodPolentz@aol.com wrote: > > I have an alternative suggestion. Those 30 year old radios don't > sound too good, never did. So, if your car is concours why don't > you just put the pos. grd. radio in the dash and call it good. I > have never seen a concours judge ask an owner to turn on the > radio to see if it worked. And, if your car is not concours, why > don't you put the old radio on the shelf and put in a modern radio > with cassette, etc. Or, I guess you could put the old radio in the > dash and wire a modern radio in a remote location so you can > listen to decent quality sound? That's just my two cents worth. > > Rod Polentz > '62 OTS |
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