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Fisher 500C,Putting in a full bridge rectifier, and new Capacitors.

Discussion in 'Fisher' started by Mikeorg, Sep 30, 2018.

  1. Mikeorg

    Mikeorg New Member

    Messages:
    42
    Location:
    OREGON
    I would like to take out the Selenium, put in a new bridge rectifier and new caps, but the way the last guy that work on this Fisher 500C has put these old cap in has me confused, it looks to me like the positive is linked up to the negative, can anyone give me a clear way the caps two 1000uf 50v are supposed to be placed in the circuit?
     

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  2. dcgillespie

    dcgillespie Fisher SA-100 Clone Subscriber

    Messages:
    9,673
    Location:
    Ball Ground, GA
    While the work is kinda goofy, the caps appear to be wired correctly. The one cap is double the normal MFD value, and I can't see the value of the other cap to know if it is too. But doubling the original value is no problem for the caps in this position. The only other deviation is that someone has played with the output tube bias dropping resistors to provide more bias voltage to the tubes. The basic wiring configuration however is correct.

    Dave
     
    Mikeorg likes this.
  3. Catmanboo

    Catmanboo AK Subscriber Subscriber

    Messages:
    483
    Location:
    Atwater, ohio
    At least 1 junk-box cap in there. ... whatever works in a pinch!
     
    Mikeorg likes this.
  4. Mikeorg

    Mikeorg New Member

    Messages:
    42
    Location:
    OREGON
    I'm taking both of these caps out and have a mached set of 1000uf 50v going in!
     
  5. Catmanboo

    Catmanboo AK Subscriber Subscriber

    Messages:
    483
    Location:
    Atwater, ohio
    That's your best bet, as they work in tandem to filter the rippled dc from the rectifier. That beat-up cap could be from an old tv or something ,who knows what it's remaining lifespan could be. If your stock rectifier is in-spec, your shot to call re: replacement as preventive maintenance, or run it until it's output starts to drop. Could take a long time for that, depending on the run-time of your 500c.
     

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