Faulty board from an electric heater

Discussion in 'General Electronics Chat' started by tpny, Dec 30, 2013.

  1. tpny

    Thread Starter Member

    May 6, 2012
    216
    0
    Hi, please see attached picture. This came from my electric heater. The lcd display doesn't come on. The 110VAC is available and goes into the board you see and out to another board to convert to 5 and 12 vdc which gets wired back to the mainboard in picture. So I see the 5 and 12vdc and 110vac available on the mainboard, but the lcd doesn't light up and the nothing is ON. Any suggestion where to check? For lack of better knowledge I tend to first blame the caps, could these big yellow square caps (3 in the picture) be faulty? They read 0.1uF 275VAC.. Thanks
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,969
    744
    You need to check the voltages on the 28pin chip, see if its got 5v on it, that will be the problem.
     
  3. Meixner

    Member

    Sep 26, 2011
    116
    21
    In the lower left corner of the photo near the fuse there is "7805" marked on the board. Check around it for voltage. Be careful if the heater does not have a power transformer.
     
    inwo likes this.
  4. inwo

    Well-Known Member

    Nov 7, 2013
    2,433
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    Wow, I looked ten times and couldn't find it.
    Good catch!
    Of course I was looking on the other left.:);)
     
  5. tpny

    Thread Starter Member

    May 6, 2012
    216
    0
    That 3 pin connector has 12vdc, gnd, 5vdc reading. So I"m good. There's no 7805 on the board, there is a marking though.
     
  6. tpny

    Thread Starter Member

    May 6, 2012
    216
    0
    5vdc is available on the board, I didn't measure on the mcu side but I'm sure power gets traced to it. I suspect the mcu (is that what it is?) is fried. If that's the case, nothing I can do to but to replace the whole heater. Why do I hate mcu's on cheap appliances.
     
  7. inwo

    Well-Known Member

    Nov 7, 2013
    2,433
    315
    Does a heater need a controller at all?

    Let-er-rip!:D
     
  8. inwo

    Well-Known Member

    Nov 7, 2013
    2,433
    315
    Is this a space heater?

    All these fancy super efficient space heaters from ads.:rolleyes:

    Show me an electric heater that's not near 100% efficient.:)
     
  9. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
    1,305
    Replace the xtal resonator (yellow blob) right next to the microcontroller. :)
     
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