Inverted Phase; Tube Green Fault - VTL S-400 II series Owner's Manual

conditions, and the amplifier may change its status in response to the new condition. In other cases the fault
will need to be attended to by the user or the dealer's technician. In all cases the fault will be detected and the
amplifier self-protected before any damage can occur.
The possible faults (and clearing actions) are as follows:-

INVERTed Phase

The up-down PHASE switch on the rear panel of the amplifier allows for switching the amplifier between
PHASE 180 (INVERT/out of phase) (down) and PHASE 0 (in phase) (up). In the down position the front
panel text will indicate the steady red INVERTed phase, and the amplifier will be phase inverting from its
input to its output.
The red INVERT text is off when the system is in the PHASE 0 state (in phase).
RS-232 command: >PHASE Queries the phase setting of the amplifier.

TUBE green Fault

The Green TUBE text indicator indicates that an output tube has a non-critical fault, such as low (or no) current
draw. The tube could be either open or out of the socket, and the autobias system has been unable to bring it up
to full power.
The tube number is displayed on the front panel display, and the top deck LED next to the indicated tube is
blinking steadily to show the exact location of the tube. The steady blinking on the open tube will continue to
blink while the amplifier is in the standby condition, or while music signal is present, where all the other LEDs
are off.
This is a warning indicator only, and the amplifier can continue to operate without the need to shut down
immediately, as balance across the output transformer is maintained with the system shutting off the
corresponding tube in the push pull pair. However the indicated tube should be changed as soon as possible, as
in this condition output power will be lowered and sonic performance will be affected.
In the case of a second green tube indicator the amplifier will immediately shut down and will indicate a red
TUBE fault, as the fault sensing system could otherwise become compromised under these conditions, and it is
not recommended that the amplifier be operated with a green fault.
S-400 Amplifier Owner's Manual 40
VTL