Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Old November 22nd 19, 08:50 PM posted to sci.electronics.repair
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Default Electric blanket controller

Gentlemen,

I refer to you this photo of the internals of a typical modern cheap and
nasty blanket controller. All the components it uses are shown on this
board: just 5 diodes, 3 resistors and some 'mystery component' whose
function is presumably to sense overheating from the two resistors it's
between and cut-back the mains voltage to the blanket itself if needed.

https://tinyurl.com/t7s6og8


Question is, what is the correct name for this 'mystery component' and
what should it read resistance-wise when cold?

Thanks!



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Old November 22nd 19, 08:53 PM posted to sci.electronics.repair
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Default Electric blanket controller


Question is, what is the correct name for this 'mystery component' and
what should it read resistance-wise when cold?


.... and (I forgot first time around)... why have they put a couple of
turns in each of the leads?



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Old November 22nd 19, 09:17 PM posted to sci.electronics.repair
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Default Electric blanket controller

Cursitor Doom wrote:

https://tinyurl.com/t7s6og8

Question is, what is the correct name for this 'mystery component'


PTC thermistor?
thermal fuse?

http://www.aolittel.com/sale-10973142-aupo-p3-f-pico-subminiature-pellet-ceramic-thermal-fuse-tf-cutoff-125c-250v-2a-axial-leaded-for-air-.html
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Old November 22nd 19, 10:11 PM posted to sci.electronics.repair
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Default Electric blanket controller

In article , says...

I refer to you this photo of the internals of a typical modern cheap and
nasty blanket controller. All the components it uses are shown on this
board: just 5 diodes, 3 resistors and some 'mystery component' whose
function is presumably to sense overheating from the two resistors it's
between and cut-back the mains voltage to the blanket itself if needed.

https://tinyurl.com/t7s6og8


Question is, what is the correct name for this 'mystery component' and
what should it read resistance-wise when cold?




It might be a simple fuse. See if the resistance is zero/near zero when
warm and cold. Can not tell from the photo, but looks tohave a 7A over
the 120 volt.


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Old November 22nd 19, 10:53 PM posted to sci.electronics.repair
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Default Electric blanket controller

On Fri, 22 Nov 2019 20:17:25 +0000, Andy Burns wrote:

PTC thermistor?
thermal fuse?

http://www.aolittel.com/sale-1097314...-subminiature-

pellet-ceramic-thermal-fuse-tf-cutoff-125c-250v-2a-axial-leaded-for-
air-.html

Bingo, Andy! Good call.



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Old November 22nd 19, 10:54 PM posted to sci.electronics.repair
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Default Electric blanket controller

On Fri, 22 Nov 2019 16:11:31 -0500, Ralph Mowery wrote:

It might be a simple fuse. See if the resistance is zero/near zero when
warm and cold. Can not tell from the photo, but looks tohave a 7A over
the 120 volt.


It's actually 2A in this case. Andy's suggestion was correct. But like
you say, the resistance should be pretty low whereas it's actually
infinite, so looks like it's blown.



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Old November 23rd 19, 12:49 AM posted to sci.electronics.repair
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Default Electric blanket controller

On 11/22/19 2:50 PM, Cursitor Doom wrote:
Gentlemen,

I refer to you this photo of the internals of a typical modern cheap and
nasty blanket controller. All the components it uses are shown on this
board: just 5 diodes, 3 resistors and some 'mystery component' whose
function is presumably to sense overheating from the two resistors it's
between and cut-back the mains voltage to the blanket itself if needed.

https://tinyurl.com/t7s6og8


Question is, what is the correct name for this 'mystery component' and
what should it read resistance-wise when cold?

Thanks!




Not sure about the name of the component, but I will say that today's
electric blankets are awfully poor made. Years ago, when I had one
while growing up, it lasted for at least 10 years before someone threw
it away during cleaning. As an adult, I purchased a Sunbeam brand about
five years ago and I've never had one last more than 6-8 weeks! The
only type of heating blanket I've found in recent times that does last
are electric throws. I have two, purchased about 5 years ago, and with
heavy use, they still work fine. Problem is that they are a bit too
small for bed use although I make them work that way.
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Old November 23rd 19, 07:34 AM posted to sci.electronics.repair
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Default Electric blanket controller

On Friday, November 22, 2019 at 11:50:53 AM UTC-8, Cursitor Doom wrote:

I refer to you this photo of the internals...


Question is, what is the correct name for this 'mystery component' and
what should it read resistance-wise when cold?


It's either an energency overtemperature cutoff (like a fuse), or a thermal
switch that repeatedly time-cycles according to the
heating/cooling time constant of its companion resistors.

It has a '2A' rating, not a temperature rating, so probably NOT
the emergency cutoff. Maybe a PTC resistor (solid state 'switch').

The diodes presumably send current to heating element A on
positive half-cycles, and heating element B on negative half-cycles
(so as to retain some function if one element fails open-circuit).
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Old November 23rd 19, 08:08 AM posted to sci.electronics.repair
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Default Electric blanket controller

On 23/11/19 5:34 pm, whit3rd wrote:
On Friday, November 22, 2019 at 11:50:53 AM UTC-8, Cursitor Doom wrote:

I refer to you this photo of the internals...


Question is, what is the correct name for this 'mystery component' and
what should it read resistance-wise when cold?


It's either an energency overtemperature cutoff (like a fuse), or a thermal
switch that repeatedly time-cycles according to the
heating/cooling time constant of its companion resistors.

It has a '2A' rating, not a temperature rating, so probably NOT
the emergency cutoff. Maybe a PTC resistor (solid state 'switch').

The diodes presumably send current to heating element A on
positive half-cycles, and heating element B on negative half-cycles
(so as to retain some function if one element fails open-circuit).

It's cactus, throw the thing out.
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Old November 23rd 19, 10:45 AM posted to sci.electronics.repair
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Posts: 10,956
Default Electric blanket controller

On Friday, 22 November 2019 23:49:28 UTC, Starfella wrote:
On 11/22/19 2:50 PM, Cursitor Doom wrote:
Gentlemen,

I refer to you this photo of the internals of a typical modern cheap and
nasty blanket controller. All the components it uses are shown on this
board: just 5 diodes, 3 resistors and some 'mystery component' whose
function is presumably to sense overheating from the two resistors it's
between and cut-back the mains voltage to the blanket itself if needed.

https://tinyurl.com/t7s6og8


Question is, what is the correct name for this 'mystery component' and
what should it read resistance-wise when cold?

Thanks!




Not sure about the name of the component, but I will say that today's
electric blankets are awfully poor made. Years ago, when I had one
while growing up, it lasted for at least 10 years before someone threw
it away during cleaning. As an adult, I purchased a Sunbeam brand about
five years ago and I've never had one last more than 6-8 weeks! The
only type of heating blanket I've found in recent times that does last
are electric throws. I have two, purchased about 5 years ago, and with
heavy use, they still work fine. Problem is that they are a bit too
small for bed use although I make them work that way.


10 years? I grew up with one several times that old.


NT


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