Two caps instead of 1 ?

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  • kaboom
    "Oh, Grouchy!"
    • Jan 2011
    • 2507
    • USA

    #21
    Re: Two caps instead of 1 ?

    Good for you Vince!

    Is that a capacitive voltage divider power supply?


    Two weeks ago, I repaired am automatic temp control board for a Whirlpool washer. This machine is from the mid 80's and a replacement board is around $110.

    It was supposed to modulate either the hot or cold water valve based on the water temp selected for the cycle. Warm is hot valve constantly energized, cold modulated; cold is cold constantly with hot modulated. Unlike 'normal' warm and cold settings, this would assure that 'warm' isn't too hot. And more importantly, that 'cold' wasn't too cold. About 10 years ago, this stopped working- 'warm' was hot & cold continuously, 'cold' was just cold.

    I found a service aid better explaining the ckt. I made a little test jig with a pot in place of the thermisor to simulate incoming water temp, and a 4W night light bulb in place of whatever valve was switched by the triac. While playing and probing around, I concluded that the LM339 quad comparator had one of its outputs 'stuck high.' This made the gate driver for the triac bias the triac constantly.

    One LM339 and 69 cents later, the board worked again and conformed to the data in the service aid. I got the '339 from ratshack years ago... I also replaced the caps.

    -Paul
    "pokemon go... to hell!"

    EOL it...
    Originally posted by shango066
    All style and no substance.
    Originally posted by smashstuff30
    guilty,guilty,guilty,guilty!
    guilty of being cheap-made!

    Comment

    • ukvince
      Learning
      • Jun 2011
      • 31

      #22
      Re: Two caps instead of 1 ?

      hi Kaboom,
      To be honest i'm not sure what it's called. It controls the motors, i quess that's what the relays are for. How they can charge £163 for one is beyond me. All the components on that board could be replaced for about £10. The hardest part was finding that capacitor. There are lots of 400v caps but it had to be rated at 400vac not 400vdc hence the one i used was 875vdc/400vac and just managed to shoehorn it in.
      It was a small project but i still get a buzz when it is working again.
      Thanks everyone for your help ....

      Comment

      • kaboom
        "Oh, Grouchy!"
        • Jan 2011
        • 2507
        • USA

        #23
        Re: Two caps instead of 1 ?

        Originally posted by ukvince
        It was a small project but i still get a buzz when it is working again.
        There's no better feeling.
        "pokemon go... to hell!"

        EOL it...
        Originally posted by shango066
        All style and no substance.
        Originally posted by smashstuff30
        guilty,guilty,guilty,guilty!
        guilty of being cheap-made!

        Comment

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