Hey guys, hope this note finds all of you well, it is
a lovely day here in MA.
Last night I install a new line voltage circuit in the
radio room for use with my new Ameritron AL-80B
amplifier, here are the details...
1). 2-pole common trip 20A breaker in the service
panel.
2). 12-2 w/Ground NM cable out of the panel, about a
15' run.
3). 6-20R receptacle in the wall, wired Black hot,
White hot (coded black), and bare copper equipment
ground.
4). I am going to replace the factory 5-15P plug on
the amplifier's power cord with a 6-15P for the 240V
service, the amplifier is rated for max 10A draw at
240VAC and will have corresponding 10A line fuses in
the chassis. So the 5-15P plug is all it needs.
So all that is well and good; now comes my need for
advice, as I have no experience with HF tube
amplifiers and tapping the transformers there in.
At that time I checked the new circuit with my DMM an
"Ideal TestPro 361" (True RMS reading). At the
receptacle on the wall the reading was 248VAC across
the two hot legs, it was 1AM in the morning so there
was no big demand on the neighborhood grid (rural,
limited house and few with air-conditioning, no
businesses, and one HV line on a dead end street).
Today it is a little after noon on a Sunday and I am
reading 244VAC at the receptacle, obviously
neighborhood demand is up compared to my early AM
check.
The AL-80B amplifier has taps for 240, 245, and
250VAC. So the question is which one to select?
Keeping in mind the local grid demands determining how
much voltage potential will be presented to me, during
the varied hours of my operation.
1.) The 240VAC tap seems out because either way you
will be hitting the amp with a 1.64% to 3.23% over
voltage.
2.) I am thinking that the 245VAC tap would be the
choice to make; the line voltage might be a bit soft
at times of high grid demand (0.4% under-voltage) but
that is awful close, 1.20% over-voltage of the 248VAC
potential during those late light hours on the low
bands shouldn't hit the amplifier to hard.
3.) The 250VAC tap also seems like a poor choice as
either way the amp with a 2.46% to 0.80%
under-voltage.
So what do you guys think, is the 245VAC tap the way
to go? Also keep in mind that I have only done two
readings, the line voltage could drop closer to 240
under further grid demand.
Peace
James - AD1L
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