Collins designed the 516F-2 for voltages less than today's typical line
voltage. This is because a certain minimum voltage is required for good
performance, and Collins wanted good performance even if the line voltage
was less than what we now consider normal (110 volts or 220 volts). The
specified voltages were actually a "minimum" voltage rather than nominal.

Line voltages were slightly less when the 516F-2 came out. And, tubes were
much cheaper.

Today, tubes are much more expensive and difficult to obtain, so it is
important to not exceed the voltages to provide maximum life for tubes.

I built my own substitute power supply for my KWM-2A. Although I have solid
state rectifiers, I have a timed delay to allow full warm up of the tubes,
prior to application. And, I monitor the filament voltages and use a
step-start. The result is that I have not had to change a tube in my KWM-2A
in about 25 years, even though I used it daily for almost 10.

73, Colin K7FM


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