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Repair to electric blanket control switch

Discussion in 'Repairing Electronics' started by julian, Nov 29, 2010.

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  1. julian

    julian New Member

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    The Morphy Richards - dual control - electric blanket has ceased working. Upon inspection I find that a component I think is a thermal fuse (V100TAM - 103 C 044 - [PS] EJET) does not pass current. I have contacted various suppliers but no one can give me an exact replacement.
    Does anyone know how to source the component?
    What do you think the current rating is?
    If I used a 10A TCO would it do the job or do I risk electrocuting myself?
    Help!
    Julian
     
  2. ben7

    ben7 Member

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    We will need to know what temperture the fuse melts at, it is very important and keeps the electric blanket from catching on fire. :eek:

    A 10amp one should be fine. ;)

    -Ben
     
  3. pfofit

    pfofit Member

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    Looks like a 103 degree Celsius thermal cutoff (TCO)
    Measure the resistance of the element. and divide by the voltage to get idea of current.
    Better to temporarily short out the TCO and measure current. Will also let you know if there is something else wrong.
    However the temperature is the deciding parameter for a thermal fuse.

    Can you show a picture?
    Is it metal with a coloured pointy end, a whitish ceramic type material that looks like a resistor or a rectangular type block with radial leads.?
     

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  4. dave

    Dave New Member

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  5. Neal

    Neal Member

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    Thought it may be 103 C, but that seems like an awfully high temp--------
     
  6. pfofit

    pfofit Member

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    The Op does not show the degree symbol but some tco's do not show it.
    It's always surprising to me the design values used in various appliances. However i go by what the manufacturer thinks is best.

    The placement of the TCO is critical and needs to be placed in the same place with the same attachment mechanisms. If it has a metal clip then it has to be reused . If it is heat shrinked in a special manner then that is duplicated. Transformer windings have them in contact with the windings taped and wrapped under the outer paper layers etc.
    Besides where/how it is physically placed or buried one also has to consider the I²R self heating affect.

    On a side note whirpool uses a 98C TCO in their dishwashers mounted on the main board in the control panel sitting in open air an inch above the board which is all under a plastic cover. When the dishwasher heats the water or during the dry cycle, steam is meant to vent from this panel although from the other end. Sometimes the vent gets gooked up with crude or the user blocks it with their butt or a towel/rag etc. This causes the hot steam (100C +) to linger around the TCO and trigger a false opening.
     
    Last edited: Nov 29, 2010
  7. julian

    julian New Member

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    Upon close inspection the 103 C does have a degree symbol next to it. The component does look like you describe - about 2mm diameter and 10 long, it looks plastic not metal. If it is the I²R effect that causes the fuse to blow then surely a higher current rating will increase the temperature it blows at!
    Ha! - I notice that it lies tightly between two resistors [brown grey red] and it was covered by a white grease. Is the heat that causes it to blow generated by them??
    If that is the case then the rating is irrelevant. Does this make sense! what do you think?
    [have a nice pic but dont know how to upload it]
    Thanks
    Julian
     
  8. pfofit

    pfofit Member

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    I said regarding temperture selection design
    And to your question, no. First it's not a fuse it's a thermal cutoff. The wax pellet inside the device is made to melt at a specific temperature and how it gets to that temperature is irrelevant to the wax.
    The higher current rating means that it will just require more current to finish it off it the external temperature does not get it first. The blanket will only draw the current it needs.
    A 130'C 2 Amp TCO is designed to open at 130'C. However if the device draws more than 2 amps then it too will open the TCO. Everything has a limit and the amp ratings is only that . You will find that the higher current TCO are larger/bigger and can be more of a problem to physically locate. If you have a short, then both a 2 Amp or a 10 amp TCO is toast.
    From my pics above the second metal one is rated at 10 A and in first pic, they are from 1 to 3 Amps in increasing physical size
    Of coarse, I didn't design the gizmo but probably yes. It's most likely part of the design, however, as stated there will also be internal heating due to the current that flows within the mechanism. You need to match it if'n you want to maintain the original safety .
    Click on Go advanced and scroll down manage attachments and then navigate to where you have it sitting on your HD with the browse button.

    cheers
    Julian , what does the label on the blanket say in regards to watts?
     
    Last edited: Dec 1, 2010
  9. Henry Gonzalez

    Henry Gonzalez New Member

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    Just a bit of warning , if the thermal cut off device is open circuit, its obvious that there was a mal function in the blanket, either was left ON for a very long time or the heating elements may have shot circuited ( not necessarily a dead short circuit) increasing the current and in turn activating the safety device.
    In my case the faulty thermal device was rated at 76 degree celsius and to ensure that the blanket had no damage a visual inspection
    was carried out, on top of that the resistance of the heating elements was measured by comparison with the other side of the blanket.
    After replacing the the faulty component the blanket was back on duty.
    Don't mess with electricity if you don't know how to do it, a new blanket is cheaper than a funeral.
     
  10. JimB

    JimB Super Moderator Most Helpful Member

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    The OP has not been seen here since December 2010, let's just put this thread to bed.

    Thread locked.

    JimB
     
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