Help diagnosing Whitfield Advantage rotary knob board

Scooter5 Posted By Scooter5, Apr 24, 2019 at 10:06 PM

  1. Scooter5

    Scooter5
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    Apr 24, 2019
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    whitfield board.jpg Good evening,
    I need help diagnosing a Whitfield Advantage rotary knob board. I know the stove works because it has a working board I have been using as comparison. Things I know are as follows.
    1. the 5.3V isolated circuit appears to be working. Jumping across output of optocouplers made no difference.

    2. relay tests good and manually closing it does nothing. If I jump across MCR100 thyristor I can push start button and will close relay, but nothing works on board and relay releases when I remove jumper.

    3. Jumping across P1081-1 transistor by MCR100 does nothing.

    4. I have taken measurements of all semiconductors both from neutral to pins and from VSS (on each chip) to pins in both AC and DC. I have found the difference between working board and bad one is the bad one is missing approximately 15v DC in locations the working board has and I cannot figure out where that source starts.
    5. I have data sheets on all components, but some I am not sure which direction power is going. For example the transistor that works the auger triac uses the collector to the triac gate, but the date sheet I have for the transistor says it is NPN.

    I see many requests for a schematic so I am uploading mine. Use it with caution, because there are variations of boards and my schematic may also have errors. There are some diodes I cant see to show direction.
    Ignore the capacitor directions, I made not attempt to figure out polarity.

    Any advice will be much appreciated.
    Thank you,
    Scooter
     

    Attached Files:

  2. bob bare

    bob bare
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    Oct 31, 2013
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    I only looked at your "tests" a little,did not research it,and do not know the control board,but seems to me you are overthinking or going around the problem.Most control boards have a "hi" voltage side,120,and a "lo" side normal 5 volt computer voltage.The transformer does the step down,and rectifiers turn it into DC.
     
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  3. Ssyko

    Ssyko
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    The triac’s do the switching for the 120vac components. The low voltage is isolated with the opto’s. So its 2 separate circuits, like Bob said. 120vac and 5-15.5vdc depending on manufacturer. The only whitfield board i ever had was the recipient of a hopper fire so it wasn’t worth the time to guess through it. But i would check the transformer and see if the windings are not shorted.
     
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  4. Scooter5

    Scooter5
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    Apr 24, 2019
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    Thank you for the replies.
    The low voltage 5.3 DC isolated circuit is working. The reason the readings are taking in AC and DC is because the rest of the board after the optocouplers has AC and DC components.
    There is a person I have seen on pellet stove forums that is knowledgeable with Whitfield boards I am hoping to receive a response from, but do not recall a user name.
    Thank you,
    Scooter
     
  5. Ssyko

    Ssyko
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    that would be Bobbare or stovenson
     
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