Advanced Functions and Diagnostics
These functions are for checking the condition of the output tubes, to determine life left. These critical
functions are necessary for the continued optimum performance of this amplifier, and if the user is not
comfortable operating them then the installer dealer or technician can perform these functions either locally
or remotely.
Function Procedure Indication
Display Tube Bias
Displays the bias settings of
each individual output tube.
Bias settings are the first
indicator of unmatched tubes,
or aging tubes, as some tubes
will require different bias than
others, and tubes will require
different amounts of bias as
they age. Use this test to group
tubes, as best performance is
achieved when tube bias values
are grouped together.
For best results, perform this
test after the amplifier has been
in operate mode continuously
for at least 1 hour.
This function is accessible in
operate mode only.
Mute the preamp to prevent
music signal from coming
through to the amplifier.
(Muting the amplifier invalidates
the tube bias test.)
Pressing the BIAS button
displays the tube number while
the button is held down. That
tube’s bias setting is displayed
for 2 seconds when the button
is released. Pressing the button
again displays the bias value of
the next tube. Every time this
button is pressed the tube
number will increment, to rotate
through the whole set of output
tubes from 01 thru 12.
RS-232 command:
>TUBEBIAS
The corresponding top deck LED
next to the tube being queried
also flashes quickly while the
BIAS button is held down, to
identify the tube indicated on the
front panel display.
WARNING: All connections and disconnection of cable to the amplifier should be done
with the amplifier powered down and the main AC Rocker switch in the OFF position.
S-400 Amplifier Owner’s Manual
VTL
37
