[Healeys] Radio, changing from positive ground to negative ground?

[Roger Grace]

Measure the current of your radio with an external batt; then look for an ISOLATED 12V  (output and input) dc to dc converter with an output matched to the input current of your radio plus 20%; connect the converter +ve to radio chassis; this should work but be sure not to mix car volts with converter volts anywhere ... ! 
rg
From: Alex 
Sent: Tuesday, October 24, 2017 5:39 AM
To: Michael Oritt ; Stephen Hutchings 
Cc: Austin Healey 
Subject: Re: [Healeys] Radio,changing from positive ground to negative ground?

Michael, it's not a matter of voltage (12V), but how much current will flow!  High current at low voltages can be destructive, even resulting in heat and fire.

== Alex in Maine
     "The Blue Mainie," 1960 Austin Healey 3000 BT7
     "Conkling," 1946 M.G. TC #1321
     Former owner 1957 A-H 100-6, 1967 A-H BJ8, 
     1965 MG Midget   ‹(•¿•)›
     http://ai2q.org/


  ----- Original Message ----- 
  From: Michael Oritt 
  To: Stephen Hutchings 
  Cc: Austin Healey 
  Sent: Monday, October 23, 2017 2:42 PM
  Subject: Re: [Healeys] Radio,changing from positive ground to negative ground?

  I believe the antenna must be shielded as well.  This happens automatically with the usual plastic or hard rubber mounting grommet but should the exterior of the antenna somehow touch either bare metal on the body or elsewhere a short will likely occur.  It's only 12 volts so it won't be harmful but it will certainly get one's attention if the connection is good enough.

  Best--Michael Oritt 

  On Sun, Oct 22, 2017 at 11:01 PM, <s.hutchings at rogers.com> wrote:

    I had an old Austin 1800 with positive ground- I just isolated the negative ground radio from the chassis and ran it as negative ground. It depends on the radio design whether you have enough room to sheath it in something like very thin plywood.

    Stephen BJ8

    Sent from my iPad

    > On Oct 22, 2017, at 1:38 PM, <glemon at neb.rr.com> <glemon at neb.rr.com> wrote:
    >
    > I used a polarity converter many years ago when I put a "modern" am fm cassette in my 67 Sprite (Pioneer KP5500, the things you remember).  The inverter ran all the time and made a high pitched slightly audible squeal.  After it drained my battery I added an inline switch.  It also would cut out for a second if there were a sudden voltage change, such as tapping the brake lights.
    >
    > I messed around with the voltage regulator to try to compensate for the voltage drop, no help, screwed that up too.
    >
    > An all (many) subsequent cars I just switched polarity, much easier and never any problems.
    >
    > Greg Lemon
    >
    > ---- Oudesluys <coudesluijs at chello.nl> wrote:
    >> There are also separate radio polarity converters around.
    >> Kees Oudesluijs
    >>
    >>
    >> Op 21-10-2017 om 10:57 schreef Bob Simmen:
    >>>
    >>> Is there a way to change an original positive ground radio to negative
    >>> ground on my BJ8?
    >>>
    >>> Thanks in advance.
    >>>
    >>> Bob
    >>>
    >>>
    >>>
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