Yep! Like Jeff said, some sort of a DC to DC thingie. Comments regarding
mechanical repair to modern electronics reminds me: RCA Colortrack TV
receiver - mid '80s model. Modularized; a problem tracked down to the tuner
control module - opened up tuner control module and found a note under the
shield that the "new" set had already been serviced before it was sold to
me. The pecker tracks therein must have been the first fix for an
"intermittent" in the module because it came clear (again) when I
reinstalled it.

Some time later, when the problem reappeared I was able to fix it with a
popsicle stick propped under the rear of the tuner control module. Now this
was "really cool" - complex electronic problem fixed with a popsicle stick!

Over the years, the module would exhibit the same problem which was handily
repaired via the popsicle stick fix. Ultimately, a stack of popsicle sticks
failed to clear the problem - like it was still intermittent, over a cycle
of months, or sometimes years.

Optovisor (finally) to the rescue revealed a tiny PCB crack around an edge
card connector on the front of the module. This was 4 or 5 years ago.
After soldering over the crack, the old RCA has given trouble-free service
as a bedroom set ever since.

Bob Swinney



"jim rozen" wrote in message
...
In article , Jeff Wisnia says...

Robert Swinney wrote:
So Jim, what are the electronics for? I sorta figured the new LEDs used
(only) appropriate dropping resistors like older conventional LEDs.

Likely it's a dc to dc converter of some sort, much more efficient than
wasting power in a dropping resistor. I'm amazed at the kind of
efficiencies I see claimed in chip manufacturer's ads these days.

Jim just confirmed what I've been saying for the last ten years or so,
repair of consumer electronics has become more of a mechanical job than
an electronic troubleshooting one. The parts themselves hardly ever fail
these days, it's mainly "loose disconnections" that keep the parts from
doing their intended tasks.

The electronics are two transistors, a couple of resistors, and a
flyback inductor, to boost the voltage so that a white LED that takes
four volts to turn on, can be run off of two AAA batteries that only
make three volts.

Now if I only could have found the loose connection that made my
daughter's cell phone stop working - not that I didn't inspect
every bit of the board under a microscope for an hour or so!

Jim


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