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. Basically the higher the current the hotter the junction, the hotter
the junction the higher the current flow. Without any checks in place the
device will get so hot it melts. The most simple solution, of course, is to
limit the output of the power supply. No matter how hot the junction gets
it can't flow any more current than the power supply can output. 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
Now while semi conductors are capable of operating across a wide range of
temperatures, the device itself might not be. 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.
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. If you do,
re-create the conditions where the radio doesn't work, power it up and wait.
Even under the coldest conditions there will be some limited current flow
which should cause the electronics to warm up and begin to work. Also, you
might try re-creating the problem and then using a space heater to warm the
interior of the car.
"David M" <NOSPAM@nospam.com> wrote in message
> On Sat, 03 Sep 2005 16:34:55 +0000, ironrod rearranged some electrons to
> > Where do you live? In extremely cold conditions transistors & IC's can
> > become "Cold Soaked" that is, the components have become so cold that
> > internal resistance has risen to the point that they can no longer
> > 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" <email@example.com> wrote in message
> > news:BjKRe.4462$oJ2.firstname.lastname@example.org...
> >> When the car heats up under the sun the in-dash radio works fine but
> > it
> >> cools down the radio will not power up. I tried replacing fuse check
> >> 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)
> T/S 53
> sled351 Linux 2.4.18-14 has been up 36 days 22:54