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• Solved! - kaaos 17:19:09 03/10/02 (2)
  In Reply to: 300B glowing red in AN Kit one posted by kaaos on March 10, 2002 at 06:31:02:

  Thank you Audiodude, Firefli and Steven Oda

  I think I found what is the problem.
  The 900ohm restors on the problematic socket are measuring somewhere around 180ohm.
  I presume that this is it, but my question is:

  I have actually two resistors conected in parallel for each 300B socket, on each resitor is written:
  W23
  1K8
  5%
  Can I replace this resistors with any other 900ohm resistor or it has to be a special one?

  Thank you
  Regards
  Goran Nikolic
  
  

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  • Re: Solved! - Eli Duttman 18:01:06 03/10/02 (1)
    In Reply to: Solved! posted by kaaos on March 10, 2002 at 17:19:09:

    2 1.8 KOhm resistors in parallel are equivalent to a 900 Ohm resistor. The reasons for using a parallel pair are to get the exact value needed and to have a sufficient wattage rating. The power dissipated by a resistor is given by: P = I^2R. The resistors should be rated for at least 2X the power they dissipate.
    
    Eli D.
    
    

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    • Thank you (nt) - kaaos 19:30:14 03/10/02 (0)
      In Reply to: Re: Solved! posted by Eli Duttman on March 10, 2002 at 18:01:06:

      (nt)
      
      

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• Re: 300B glowing red in AN Kit one - kaaos 17:17:50 03/10/02 (0)
  In Reply to: 300B glowing red in AN Kit one posted by kaaos on March 10, 2002 at 06:31:02:

  Thank you Audiodude, Firefli and Steven Oda

  I think I found what is the problem.
  The 900ohm restors on the problematic socket are measuring somewhere around 180ohm.
  I presume that this is it, but my question is:

  I have actually two resistors conected in parallel for each 300B socket, on each resitor is written:
  W23
  1K8
  5%
  Can I replace this resistors with any other 900ohm resistor or it has to be a special one?

  Thank you
  Regards
  Goran Nikolic
  
  

  ---
• Re: 300B glowing red in AN Kit one - audiodude 11:51:07 03/10/02 (0)
  In Reply to: 300B glowing red in AN Kit one posted by kaaos on March 10, 2002 at 06:31:02:

  Check the cathode bias resistor and the bypass capacitor. Note that if this cap needs replacement it should be replaced with a part rated at 100V or greater. Also check the coupling capacitor for leakage - there should be little or no dc present at the grid of the 300B.

  Kevin
  
  

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• Re: 300B glowing red in AN Kit one - Firefli 06:47:17 03/10/02 (1)
  In Reply to: 300B glowing red in AN Kit one posted by kaaos on March 10, 2002 at 06:31:02:

  Check the cathode resistor. If it died then it could be passing WAY more current through the tube than the tube was intended to, and could cause the plates to glow red. (If the resistor looks ok, measure the amount of voltage it is dropping - I would guess the voltage should be somewhere around 60-75 volts for a 300B)

  The other possibility I can think of is that you power supply went berserk and is now giving you a much higher B+ than what belongs there.
  
  
  
  My System and DIY Projects page
  
  

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  • Re: 300B glowing red in AN Kit one - steven oda 09:37:46 03/10/02 (0)
    In Reply to: Re: 300B glowing red in AN Kit one posted by Firefli on March 10, 2002 at 06:47:17:

    Firefli,

    Not familiar with this amp. Does it have a bypass cap (across the cathode tied resistor), on the cathode? If this pops---the bias will be out of whack.
    
    

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