Output Tubes

6GW8 6L6GC EL34 -- 6CA7 EL84 -- 6BQ5 -- 7189 6550A 7591A 7868

 


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Last Edited:
12-Sep-2004


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 EL34's.

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.

Typical Scott Amplifier (with "Split-Load" Phase Inverter) Schematic -- Type 208

 

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