Induction Cooktop Repair Help

Discussion in 'General Electronics Chat' started by wess.vic, Dec 27, 2015.

  1. wess.vic

    Thread Starter New Member

    Dec 27, 2015
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    I recently was given a vollrath 240volt induction cooktop that didn't work. I tried turning it on and it blew apart the fuse every time. I then knew there had to be a serious short in it to have such a high in rush current to explode the fuse ceramic casing. I then did some further investigating and found one out of the three transistors for the coil was blown out the back. I soldered in a new one and a micro controller for the transistor just in case it was faulty to. I then attempted to start it again and it still blew a fuse. I then did some metering and found the circuit on the motherboard where the ac is changed to DC through a solid state rectifier semiconductor. The dc voltage ran to a current sensing transformer. I looked over the transformer and realized the 240v going in was just a large piece of wire holding it in. But it also crossed the legs at this point. So I decided to remover the transformer and then start it. It worked but since the transformer was removed the thermistor micro controller were not receiving any voltage. I then bought a new transformer soldered it in and it still doesn't work. I then came to the conclusion that the bridge rectifier was the malfunction and was not producing a dc current. But before I bought anything more I wanted to hear someone else's thoughts on what it could be thanks, victor
     
  2. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Sounds like a bargain so far. Don't burn your house down or you will have a really good story to tell about your gift.
     
  3. wess.vic

    Thread Starter New Member

    Dec 27, 2015
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    Is there any advice or help you can give me on it?
     
  4. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Make an estimate of how much you think it will cost to repair. E.g. $300

    Divide that number by your probability of success (e.g. 30%), $300/0.30 = $1000.

    Check the price of a used one from a reputable shop (and a new one).

    Bring it to the junk pile. Sell the valuable bits on eBay (if you are sure they work, or if you are willing to give refunds).
     
    sivark1980 and Johann like this.
  5. sailorjoe

    Member

    Jun 4, 2013
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    The second photo shows only two diodes, so a full wave rectifier, but not a bridge rectifier. Maybe the other diodes are somewhere else on the board. I found this schematic for a Vollrath cooktop, but I'm not sure it's exactly your model. Poke around, though.
    http://openschemes.com/2010/12/09/circuit-analysis-of-the-1-8kw-induction-hotplate/
    Not sure exactly what model number you have, but I found these docs.
    http://www.webstaurantstore.com/documents/pdf/osi_mirgebuffetinductionwarmer_manual.pdf
    http://www.webstaurantstore.com/doc...onmiragebuffetwarmer_l36009_en_2015-02-26.pdf
     
  6. wess.vic

    Thread Starter New Member

    Dec 27, 2015
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    There's two diodes and then there is a semiconductor with 4 pins. Ac in dc out. Here's a data sheet on that bride rectifier. In the pictures right beside the transistors you can see were I took it off. GBJ25J semtech rectifier
     
  7. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    A gadget every husband should have :).
     
  8. Ramussons

    Active Member

    May 3, 2013
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