VTL S-400 II series Owner's Manual page 54

4. Plugging in a new tube:
6.
For the larger Power tubes, there is a locating pin in the middle of the tube (8 pin octal tubes).
Make sure that these locators go into the side of the socket that matches. Press the tube firmly
into its socket, using a gentle force and a slight "rocking" motion. When the tube is properly
and completely inserted into the socket it should be firmly seated and does not give in to any
S-400 Amplifier Owner's Manual
VTL
Hold onto the upper portion of the tube towards its tip. Lower the
tube onto the socket, making sure that the pins from
the tube match the holes in the socket.
5.
For the smaller input tube, there are two pins on the
tube, which are spaced at a wider distance from each
other than the rest of the pins (9 pin miniature
tubes). Press the tube firmly into its socket, using a
gentle force and a slight "rocking" motion. When
the tube is properly and completely inserted into the
socket it should be firmly seated and does not give
in to any movement at all when you try to rock it
gently. If the socket appears loose and not making
contact with any or all of the tube pins, contact VTL
for help.
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