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
The World Contest Station Database, updated daily at www.conteststations.com
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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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