Bud,
Although I do read 12v DC on the meter connected between the radio 12v line and
the
radio chassis, continuity tests to a very high resistance: almost no
continuity. I
assume any of these anomalies are back roads the meter finds through the radio
circuitry... but, returning to the original question; can you describe a
procedure to
trouble shoot this?
Jim
Bud Krueger wrote:
> Jim,
>
> It's a fairly simple electrical situation. There is continuity between
>the
> power input wire of the radio (tied to +12v) and the radio's chassis. Since
>there
> is no current being drawn, there is nothing else to drop the 12 volts across
> except the air gap between the radio chassis and the negative side of the
>power
> source, whicjh happens to be connected to the car's body. The radio is
>acting as
> if it's a very high value resistor.
>
> Bud Krueger (EE)
>
> "James H. Nazarian, Ph.D." wrote:
>
> > The car could be a reclassified '66, or the previous owners could have done
>a
> > modification, or the title could have been lost and replaced by a newer one,
> > etc.
> >
> > The question is still, "why does he measure 12 volts from the radio chassis
>to
> > a car body ground?" He should be displaying 0.000 vDC. His reading indicates
> > either an internal radio short, or a polarity error in the car. How is the
> > battery connected? Is the + terminal connected to the starter or the
>chassis,
> > or is it the negative terminal of the battery that is connected so?
> >
> > Jim
> >
> > Lawrie Alexander wrote:
> >
> > > Paul, I'm afraid your supposition is wrong. MGBs changed to negative
>ground
> > > at the end of the 1967 model year.
> > >
> > > Lawrie
> > > British Sportscar Center
> > >
> > > -----Original Message-----
> > > From: Paul Nelson <ya632@victoria.tc.ca>
> > > To: mistebar@juno.com <mistebar@juno.com>; MGS@autox.team.net
> > > <MGS@autox.team.net>
> > > Date: Friday, January 28, 2000 9:52 PM
> > > Subject: Re: Radio
> > >
> > > >At 20:43 1/28/00 -0800, mistebar@juno.com wrote:
> > > >>I was just going to do a simple project on our 1968 MGB-GT and put in a
> > > >>radio. After seeing the comments, I think I need help. I replaced the
>old
> > > >>radio with a new one using the same wiring. The light on the unit
> > > >>"pulsates", but does not turn on. I don't know if the antenna is
>grounded
> > > >>or not. When I touch the radio body with a voltmeter and ground it,
>there
> > > >>is 12 volts. What am I doing wrong?
> > > >
> > > >
> > > >Seems like the 68's were still positive ground, weren't they?
> > > >Paul
> > > >
> > > >
>
> --
> Bud Krueger
> http://home.ici.net/~bkrueger/
> 52TD
> 77MGB
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