Jim,
Something's got me puzzled (not unusual). I thought that the original
symptom was
that 12v was being read between the radio chassis and the car's ground. Can
someone
please restate the symptoms?
Bud
"James H. Nazarian, Ph.D." wrote:
> 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
--
Bud Krueger
http://home.ici.net/~bkrueger/
52TD
77MGB
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