Karl,
The main cause of damage to the band switch in the SB220 is
Parasitics! These parasitics get into the fingers of the operator
who is trying to tune the SB220 and causes him/her to rotate the
band switch instead of the loading cap while full drive is applied.
The resulting arcing and sparking converts part of the switch to a gas
which is inhaled by the operator who has just had a sudden rather
sharp intake of breath. This gas remains in the operators system
for years, even decades, and eventually causes the operator to do
the same thing.
Most operators never realize the physical layout of the SB220
front panal is the primary cause of these parasitic infections of
the fingers.
Seriously, show me a longtime SB220 owner who says this has never
happened to him and Ill show you someone with a 20 year old virtually
unused amp.
73, Bob, W5AH
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