Re: Suspension losses

On Fri, 10 Jan 2025 20:01:26 -0500, Frank Krygowski
<frkrygow@sbcglobal.net> wrote:

Two days ago, my kid asked me to figure out why an electric blanket
wasn't working. The controller refused to turn on. I opened it and
confirmed that it was getting supply voltage. Beyond that, the pile of
dozens of surface mount electronic components was incomprehensible to
me. I suspect Jeff might have been able to diagnose it, but not me.
Here's a photo:
https://www.flickr.com/photos/16972296@N08/54259119364/in/dateposted-public/

I don't think I can do much with just a photograph.  If you have the
maker, model and FCC ID number, I can do better.  Also, some
indication of what it does when the power is applied, such as do the
LED's light.  If the don't light, try again in the dark and see if
they partially light.

Looking at the PCB components, I would guess it's 2000 to 2010
vintage.  In other words, it's old.  I can't read any of the part
numbers from the photo.  If the SOT-24 package (probably a PIC
Microcontroller) has a date, that would determine the age.  Looking at
an enlargement of the photo, I notice that some of the components
(LED's and pushbutton switches) were hand soldered.  Enlarging the
photo showed several possible places where the soldering looks like a
volcano with a black annular ring around the center component lead.
That's about all I can do with just a photo.

I know electric blankets are old technology. I know they functioned well
for decades with maybe a rheostat and perhaps a couple of other
components. Why add unrepairable complexity?

I don't want to write a lengthy essay on topic.  Your rheostat
probably was fine for mid 20th century technology, but would never
pass the safety standards that followed.  Those safety standards were
there for a good reason such as killing the customer by fire or
electrocution.  The rheostat design has exactly one feature, which is
to manually adjust the temperature.  If you want more features
(overload disconnect, timer, twin bed control, fuzzy logic control,
etc) electronics is required.

Incidentally, I've had several occasions where customers demanded
their old and reliable computer back, usually because they were
allergic to reading and following the instructions.  Eventually, all
of them went back to the latest greatest electronic model because the
old and reliable one was slow, difficult to use, or didn't do
something they needed.  That's the real problem with technology.  It's
really difficult to go back to primitive.

--
Jeff Liebermann                 jeffl@cruzio.com
PO Box 272      http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann      AE6KS    831-336-2558