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Bleeder resistors

Discussion in 'Amplifiers' started by 238, Nov 22, 2021.

  1. 238

    238 Active Member

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    Putting bleeder resistors on old Maco's. Wondering what size would be best. Capacitors are 100uf x 450 volts. Jim/238


     

  2. nomadradio

    nomadradio Analog Retentive

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    The three-filter Maco board we sell on fleabay uses 220k 2 Watt. Or 240k when Mouser runs out.

    A smaller resistance value will speed up the bleed down. If you want to use 100k, it should be rated at 5 Watts.

    It's a tradeoff between bleedoff speed and the power dumped by each resistor. A 330k or 470k runs cooler, takes longer.

    Most important reason is to equalize the voltage across each cap in a series string. Just gotta use the same resistance for each bleeder.

    73
     
  3. 238

    238 Active Member

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    OK Thanks. Jim/238
     
  4. 238

    238 Active Member

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  5. 238

    238 Active Member

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    I am not always sure what kind of resistor to use. Would it be best to use metal film or carbon film or carbon compose. I have 390k 3watt metal film and some carbon 470k 2 watt. Witch would be best? Jim/238
     
  6. nomadradio

    nomadradio Analog Retentive

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    Carbon film and metal film tend to have stable resistance value. Wirewound is fine, but hard to find in high resistance values.

    Carbon-composition resistors not so much. A distant second best as a bleeder IMHO.

    73
     
    NZ8N likes this.
  7. 238

    238 Active Member

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    OK Thanks Jim/238
     

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