[AMPS] Purpose of CW/SSB switch

[John Nelson]

Message text written by "Richard W. Ehrhorn"

>But experience over the first few years indicated that hardly anyone ever
used the LO position. We've left it in the 87A simply so as not to make an
unnecessary and potentially confusing change that might engender the
question, "How come MY new 87A doesn't have a HI/LO switch like
Charlie's?"<

Given our lower power limits in the UK, I guess I ought to use it then <g>.


You mentioned transformer and tube seal cooling in another post. I added
the optional external Muffin fan to my 87A before even switching it on, for
that very reason. Tube life is directly proportional to temperature, other
things being equal, and with a 50Hz mains supply I expected the blower to
be less effective than with 60Hz. Being in the airflow inlet path, it also
seemed reasonable to suspect that the transformer would run cooler as well.
At full power I measured about 25 degrees C difference in exhaust air
temperature with and without the Muffin, which probably translates to at
least that at the seals.

With a filter on the inlet fan as well, it's remarkable how clean the
amplifier stays internally. 

John Nelson
GW4FRX  

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