Re: Need HELP with 2002 Mustang in-dash Radio Power Issues
- From: "ironrod" <cmuza@xxxxxxxxxxxxxxxx>
- Date: Mon, 05 Sep 2005 17:25:11 GMT
Now you begin to see the difference between a tech (me) and the engineer.
Because car radios have to live in the enclosed environment of a car,
complete with their heat catching, solar panel, greenhouse glass window
arrangement, things getting to hot are much more likely to occur than things
getting to cold, (which could only happen during certain times of the year
in certain geographic locations.) Heat rejection would be a design priory,
whereas cold performance would be just an afterthought. I agree that cold
soak probably isn't the most likely cause, however the symptoms given by the
OP were a text book example of the phenomenon. Which is why my first
question was, 'were did he live?'.
You stated "But that [cold soak]would not occur unless the temperature is
decades below zero." This isn't necessarily true, remember most IC's
operate at 5 volts, every time you cross a junction you drop between .2 to
..5 volts, it would only take a very slight increase in resistance of several
components before the overall load was so great that 5 volts wasn't enough
to get the job done anymore.
Here is an interesting test, if you live in one of the colder areas of the
country. Take a cheep transistor radio, place it inside a plastic bag then
leave it outside, in the shade, overnight when the temperature is expected
to drop below zero. Turn it on and count the seconds from when you hit the
switch until it starts playing.
"David M" <NOSPAM@xxxxxxxxxx> wrote in message
news:pan.2005.09.05.12.19.29.781917@xxxxxxxxxx
> On Mon, 05 Sep 2005 07:05:39 +0000, ironrod rearranged some electrons to
> form:
>
> > Well lets see, I've been pushing 'trons through wires for almost 30
years
> > now, so I'm reasonably confident that I've got the basics right. In
> > extremely cold conditions, approaching absolute zero, resistance drops
to
> > near nothing. In the real world the hotter the junction of the semi-
> > conductor the greater the current flow. Conversely, the lower the
> > temperature the less current flow across the junction. Now in the real
> > world there is a condition designers have to deal with called "thermal
> > runaway" and it is a real problem in high powered circuits that get too
> > warm.
>
> That's a different mechanism... the increased temperature knocks more
> electrons loose from the semiconductor. OK, technically I guess that
> would qualify as "lower resistance" (at least at your meter test points).
>
> > Now jump to the other half of the spectrum where the
> > junctions are abnormally cold. Your power supply with its limited
> > current might not be capable of generating enough power to meet the
> > greater demand caused by the colder junctions.
>
> But that would not occur unless the
> temperature is decades below zero.
>
>
> >Most electronic
> > devices are designed to operate at "room temperature". Devices that are
> > intended to be used in extreme conditions are built much differently. In
> > some cases, I've seen environmental design problems where the best
> > solution was to create an artificial environment and use "off the shelf"
> > components.
>
> Most automotive electronics is designed to handle a much wider range
> of temperature than consumer electronics.
>
> > Now, you never did mention if you lived in a cold climate or not, if you
> > don't then obviously the problem can't be cold soaking.
>
> I'm not the OP. But I would still suspect a simpler solution,
> like a loose connector contact (heating up and expanding).
> Connectors have a higher failure rate than semiconductor
> junctions.
>
>
> >
> >
> > "David M" <NOSPAM@xxxxxxxxxx> wrote in message
> > news:pan.2005.09.04.01.37.56.291728@xxxxxxxxxx
> >> On Sat, 03 Sep 2005 16:34:55 +0000, ironrod rearranged some electrons
> >> to form:
> >>
> >> > Where do you live? In extremely cold conditions transistors & IC's
> >> > can become "Cold Soaked" that is, the components have become so cold
> >> > that
> > their
> >> > internal resistance has risen to the point that they can no longer
> > conduct
> >> > electricity.
> >>
> >> Ummm... where did you get that information from? Oh, I see, you pulled
> >> it from your a**.
> >>
> >> Electrical resistance of metals and most semiconductors goes DOWN with
> >> temperature, not up.
> >>
> >> Commercial semiconductors will perform within specifications from
> >> 0-70C. Industrial rated semiconductors will perform within
> >> specifications from -40 to 85C; automotive electronics should operate
> >> within that range.
> >>
> >> More likely the problem is a bad connection on the unit.
> >>
> >>
> >>
> >> > "MS" <nospam@xxxxxxxxxx> wrote in message
> >> > news:BjKRe.4462$oJ2.2836@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> >> >> When the car heats up under the sun the in-dash radio works fine but
> > when
> >> > it
> >> >> cools down the radio will not power up. I tried replacing fuse
> >> >> check
> > the
> >> >> wire harness etc. but can resolve this issue. Any advice will be
> >> >> highly appreciated.
> >> >>
> >> >> Thanx.
> >> >>
> >> >> Please drop me a line at vocalglobe//at\\hot mail//dot\\com
> >> >> (remove the //\\)
> >> >>
> >> >>
> >> >>
> >> --
> >> David M (dmacchiarolo)
> >> http://home.triad.rr.com/redsled
> >> T/S 53
> >> sled351 Linux 2.4.18-14 has been up 36 days 22:54
> >>
>
> --
> David M (dmacchiarolo)
> http://home.triad.rr.com/redsled
> T/S 53
> sled351 Linux 2.4.18-14 has been up 38 days 9:37
>
.
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