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Old 02-13-2021, 07:30 AM   #1
Sirgu
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Default Identifying THT resistor value + other Qs. [Electric blanket controller repair]

Hello,
I hope this fits well into "weird devices" category.

Please... anyone that knows better the science of resistors. Everything is on pictures.
Stuff written in green boxes are official values accordingly the packages and datasheets. The rest is the rest.
All I can add is that the subject`s background colour behind stripes is blueish light gray. As resistor #2 in the row is rather beige and physically smaller, I think it`s not right replacement for the main issue.

As I didn`t had resistors #1 to #4 on hand reach at first place, I quickly learned hard way that 500mW or either carbon film type resistor is not a way to go there.

I have a slight hunch that the subject might be 2W and metal oxide film due to similarities of this:
https://projectpoint.in/index.php?route=product/product&product_id=501648635957
... yet again some 3W variants look the same as well:
https://www.amazon.com/uxcell-50pcs-.../dp/B07GMZDBNJ
So I`m puzzled.

IF 3W would be right way to go - could I use my #4 for replacement even though its wirewound type of resistor.
Is there`s any significant difference between resistor materials type in this context?

Secondly.
What would you do with the burn mark on PC board? Luckly the tracks are on the other side and not damaged. I applied some kapton tape on the spot before new resistor replacement.

.....
Yes, the electrolytic capacitor is replaced as well. And atm I`m troubleshooting those yellow MPX X2 polypropylene capacitors as well, although it`s not shown on that second picture collage. Just to be sure of everything.

Thanks in advance!

Attached Images
File Type: jpg pic collage 1 [1500x2000pix, 96res].jpg (2.39 MB, 55 views)
File Type: jpg pic collage 2 [2000x1500pix, 96res].jpg (2.49 MB, 56 views)

Last edited by Sirgu; 02-13-2021 at 07:51 AM..
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Old 02-13-2021, 11:03 AM   #2
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Default Re: Identifying THT resistor value + other Qs. [Electric blanket controller repair]

The resistor is likely a 1 watt, Some manufacturers resistors are smaller in size for the same wattage. Mount the resistor above the board so it is no longer touching and it will have better heat dissipation. Did you find the cause of the open resistor or was the original not open? The one you are asking about is likely a 1 watt metal film flame proof, I would use #1,2 or 3, You can use #4 if you have room,

Last edited by R_J; 02-13-2021 at 11:08 AM..
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Old 02-13-2021, 12:02 PM   #3
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Default Re: Identifying THT resistor value + other Qs. [Electric blanket controller repair]

it's a 1w FLAME-PROOF resistor.
it's big because the oxide track is not continuous - it's a spiral so it can go open-circuit with minimal heat.
that's also why it is dipped in gray cement instead of paint.
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Old 02-13-2021, 02:36 PM   #4
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Default Re: Identifying THT resistor value + other Qs. [Electric blanket controller repair]

I think there is another bad part that cooks this resistor? Is it for a snubber or capacitive-power? Where is the triac I would check it.

There is a wide variance in the size of power resistors, a big game to make the smallest power resistor with the highest power rating. I compared dozens of different ones and realized it will drive you crazy.

A resistor manufacturer will offer a "mini size" for the same power rating, but they operate much hotter.
The larger the resistor is, the greater the heat dissipation. The better the materials (cement verses epoxy, wirewound verses film, copper leads verses FeCu) the hotter it can go.
I don't think you can judge power resistors on size nowadays.
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Old 02-13-2021, 03:32 PM   #5
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Default Re: Identifying THT resistor value + other Qs. [Electric blanket controller repair]

Thanks everyone! It broadens my knowledge a lot.

R_J - Yes, this original main issue resistor is open. And the burn mark is seemingly a long-term result. Not a sudden cause of resistor failure.
And there`s plenty of space to solder any of them there.

stj - #2, #3 and #4 also have this kind of hard matt coating while #1 is glossy paint (or epoxy for that matter). I never knew the considerations for materials used for finishing. Likewise I don`t know much of a difference of resistor type technologies.

redwire - Oh my, thanks for the input! There`s so much to discover. Snubber vs capacitive-power - How can I find out?

So... putting this all together my #2 seems almost like a replacement but probably it will heat up faster and will eventually fail later.
I am assuming that:
1.) Wattage value can be exact OR bigger (if it physically fits) but never smaller than original.
2.) Whereas `flame proof` type is a must accordingly the context.
3.) Plus physical size should be at least the same up to its values for better cooling.
[Correct me if I am wrong in any aspects.]

.....
As follow-up question:
-This polypropylene capacitor needs to be replaced, right? As it`s capacitance (exactly -20% of 1.0F) is lower than stated capacitance tolerance (10%). Also resistance slightly out of range.
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Old 02-14-2021, 07:00 AM   #6
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Default Re: Identifying THT resistor value + other Qs. [Electric blanket controller repair]

Quote:
Originally Posted by redwire View Post
... Is it for a snubber or capacitive-power? Where is the triac I would check it. ...
There are four triacs / transistors in this pcb design.
Two of them read:
MAC
97A6
13H


One is:
13001
98T


And the last one:
A1015
GR011


Make and model of thing itself (if it helps anyhow):
Rubicson KDA6-FT electric blanket
[some pictures here]

Controller looks as following:
https://www.youtube.com/watch?v=5K5p7bOWtNo&ab_channel=Per-GunnarH.%C3%85gren
Someone has done curious teardown whereas those triacs and the rest is pretty clearly seen as well. The misbehaviour of controller LED`s in the video are the same as my unit (stating that smth is wrong) but seemingly his big grey resistor next to "S" marking on top of black wire is not burnt and the stripes colour code is totally smth else than mine.
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Old 02-14-2021, 07:14 AM   #7
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Default Re: Identifying THT resistor value + other Qs. [Electric blanket controller repair]

some data
Attached Files
File Type: pdf 2SA1015.pdf (116.3 KB, 3 views)
File Type: pdf st13001.pdf (162.3 KB, 3 views)
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Old 02-14-2021, 11:11 AM   #8
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Default Re: Identifying THT resistor value + other Qs. [Electric blanket controller repair]

Here is the MAC97A6
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Old 02-14-2021, 11:20 AM   #9
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Default Re: Identifying THT resistor value + other Qs. [Electric blanket controller repair]

where does that microcontroller get 5v??
a zener diode??
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Old 02-14-2021, 11:51 AM   #10
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Default Re: Identifying THT resistor value + other Qs. [Electric blanket controller repair]

Quote:
Originally Posted by Sirgu View Post
***-This polypropylene capacitor needs to be replaced, right? As it`s capacitance (exactly -20% of 1.0F) is lower than stated capacitance tolerance (10%). Also resistance slightly out of range.
I would recommend replacing capacitor scenes you have one on hand
I would also recommend when you put the new resistor on the board do not mount it flush to the board leave a space between the board and the resistor so does not keep burning the board
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Old 02-15-2021, 04:59 AM   #11
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Default Re: Identifying THT resistor value + other Qs. [Electric blanket controller repair]

Can you attach good clear high res straight shots of the whole top and bottom side of the board?
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Old 02-15-2021, 03:45 PM   #12
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Default Re: Identifying THT resistor value + other Qs. [Electric blanket controller repair]

Sure!
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Old 02-15-2021, 03:48 PM   #13
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Default Re: Identifying THT resistor value + other Qs. [Electric blanket controller repair]

Quote:
Originally Posted by stj View Post
where does that microcontroller get 5v??
a zener diode??
This little fellow?
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Old 02-15-2021, 04:57 PM   #14
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Default Re: Identifying THT resistor value + other Qs. [Electric blanket controller repair]

I suspect there is a problem with the blanket or wiring to the blanket that caused the controller to fail. If the led's are flashing the same way as the video, it indicates there is no blanket connected, no load and no feedback/temp control. The ic is likely a PIC microcontroller

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Old 02-15-2021, 05:18 PM   #15
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Default Re: Identifying THT resistor value + other Qs. [Electric blanket controller repair]

I wonder if you could not test the blanket controller by using a 100 watt incandescent light bulb but you would probably need to light bulbs the terminal marked “S” that this might either common or temperature sensor but unless you reverse engineer it you would not know for sure

Last edited by sam_sam_sam; 02-15-2021 at 05:21 PM..
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Old 02-16-2021, 03:20 PM   #16
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Default Re: Identifying THT resistor value + other Qs. [Electric blanket controller repair]

Quote:
Originally Posted by R_J View Post
I suspect there is a problem with the blanket or wiring to the blanket that caused the controller to fail. If the led's are flashing the same way as the video, it indicates there is no blanket connected, no load and no feedback/temp control. ...
Well that`s a yes and no.
-Yes, undoubtly I cannot be sure at this point that balnket is totally okay. All I know that its wiring is continuous circuit without any drawbacks while moving, bending blanket anyhow. But still suspicious about its wiring resistance change over time when material temperature rises or drops.
-On the other hand - No! Those LEDs flasing like that are not indicating the absence of blanket. I remember when the controller was still in working condition you could set the power and timer even though when blanket was not connected in socket with it. So I assume the turbulence of LEDs is a sign of ANY kind of issue on component basis - the situation were customary end-user should stop searching the cause of wrong use and trash the unit to avoid further dangers.
Unfortunately I`m not the one.

Last edited by Sirgu; 02-16-2021 at 03:22 PM..
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Old 02-16-2021, 04:10 PM   #17
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Default Re: Identifying THT resistor value + other Qs. [Electric blanket controller repair]

Some notes:

The printings on PCB in video read
E199273
PCEM-1
94V-O
ROHS

which are the same as mine,
then on the other edge
KDA6-2015
wheras mine reads
KDA6-2012-04
2013-06-03


Then pause video at 5:20 and the colour code for the "S" big resistor seems like red-red-gold-silver = 2.2Ω 10% ?
(The rest set of big components look the same as far as eye can tell.)

Could it funnily be like few years later they found out that 2.2Ω 10% is suitable there instead of 10Ω 5% ??
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