[Amps] Fw: Fan for SB220

Mitch Cox ww4cox at embarqmail.com
Sat Dec 18 10:54:45 PST 2010

Not to try to be argumentative but this only proves the bare minimum of cooling that exists under the tube deck. If you doubt this, turn the fan off and see how long the solder lasts in any of the pins. If you have a slightly resistive connection with enough air, chances are you would never have known it.
  ----- Original Message ----- 
  From: Pete Smith 
  To: amps at contesting.com 
  Sent: Saturday, December 18, 2010 1:33 PM
  Subject: Re: [Amps] Fw: Fan for SB220

  Just one minor quibble - the first two inches of the top rear portion of 
  my SB-220's RF cage is not open, presumably to make sure that the air 
  from the fan at least starts out in the right direction.  The only 
  thermal problems I have had with my amp was the melting of the solder in 
  the filament pins of the  tubes.  The explanation I have heard for this 
  has nothing to do with cooling air or the lack, but rather to resistive 
  heating due to a slightly resistive connection between the pins and the 
  socket clips.  After re-soldering the pins, I polished their outer 
  surface and then swapped the clips for those on two of the three grid 
  pins.  No problems since.

  73, Pete N4ZR

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  On 12/18/2010 1:20 PM, Mitch Cox wrote:
  > The cooling on a standard SB-220 is a hit or miss proposition at best. You have a large fan blowing at 2 tubes without anything directing or channeling airflow with a completely open top letting the purposed airflow from the fan escape right through the roof of the amplifier before it even reaches the tubes.
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