Beam Power Output tubes drive the large output transformers that are directly connected to your
amplifier or receiver's speakers.
In Vintage H.H. Scott products, output tubes are typically Beam Power
Pentode tubes. The most popular tube families found in Scott gear are: 7591, EL84, and
On the larger Octal-base tube types (typically, 7591 and EL34's), make sure the locating
pin (key) is intact. If it is not, and you are unsure as to how to position
the tube -- DO NOT USE THE TUBE! (The pin-key is designed to permit proper alignment
of the tube into the socket -- mis-orientation could
cause extensive damage!)
Many tubes are designed to have one or more pins internally connected (shorted)
together. If the tubes are inserted (positioned) incorrectly in their
sockets, you could seriously damage the amplifier.
Power tube life is highly dependent on proper bias adjustment, cooling,
component matching, speaker impedance loads, gain levels and duration of playing time (do not run
your vintage tube equipment unattended.)
When replacing power tubes, it may be necessary to re-bias your amplifier.
Biasing is setting the correct voltage across the grid of the output tube.