> Rich said:
> "I do not agree. Rotating the bandswitch in a properly tuned 220
> results in a reduction in peak-V across the Tune-C and the
> bandswitch. in my opinion, SB-220 bandswitches typically arc from
> the intermittent parasite at 110mHZ. The arc is the result of 110MHz
> energy not being able to reach the load through the low-pass tank and
> running amok."
> I reapired a SB-220 a few years ago that suffered bandswitch failure when
> the owner did exactly that - turned the bandswitch instead of one of the
> tuning controls. I mentioned it at the time and Rich questioned my
> veracity. I was not there and only can convey what my friend told me and
> I observed.
> It seems to be human nature to pass the causes of damage to one's own ham
> gear as the fault of the design of the gear or the fault of someone else
> rather than an error of the operator, so I cannot believe that a friend
> would admit the he made a stupid mistake rather than blaming the equipment
> design - if he had the opportunity. Now, he could have lied to me because
> he thought it was better to make a mistake in tuning the rig than to admit
> he purchased an amplifier that was not adequately protected from
> parasitics - or to admit that he was operating an SB-220 without the Rich
> Measures protection circuit - but I am more inclined to think that his
> statement that the damage to the bandswitch occurred at the exact moment
> that he turned the bandswitch instead of the tuning control was true.
> My observation when I received the amplifier was that the bandswitch was
> indeed damaged.
> I also have an observation on the statement by Rich about "Rotating the
> bandswitch in a properly tuned 220". There is an assumption that may not
> be valid in his statement. If the operator turns the bandswitch by
> accident instead of the tuning control, that is an indication that the
> amplifier is not properly tuned. If it was properly tuned, the operator
> would not be tuning it. So, the basic assumption of Rich's statement is
> based upon a fact which is not likely true.
> Colin K7FM
Amps mailing list