WARNING: Do not clear the fault and re-power the amplifier without first replacing the faulty
output tube, as doing so could potentially damage the circuitry.
Reset High Current Tube Fault
If the fault indication corresponds to the High Current Tube fault with all LEDs front panel LEDs off and a solid
green LED next to the output tube on the deck, replace the faulty tube with a known good tube of the same type.
Check the Plate and Screen fuses to see if they are good, and replace if necessary. Re-power the rocker switch to reset
the fault condition and re-power the amplifier.
Clearing a green tube Fault
Turn off the amplifier with the Power button on the front panel and remove the cage of the amplifier following the
steps listed in section 8.3.
Replace the indicated tube with a new tube, and re-power the amplifier. The amplifier will automatically re-bias the
tubes and if all tubes are drawing current properly then the green tube fault will be cleared.
The tubes used in your MB-450 Signature monoblock Amplifier are specially matched and tested for
best performance. Please contact your VTL dealer or VTL factory service department to order the
matched replacement tubes.
WARNING: use only tube types and tube brands that are recommended by VTL.
VTL specified replacement tubes are available from your authorized VTL dealer or
the VTL factory service department. Any damage incurred to units that use non-
VTL approved tubes will not be covered under the warranty.
Trigger functions
For remote controlled convenience this amplifier offers 3 x 12V triggers to toggle the Power, Mute and Mode
functions that are on the front panel of the amplifier for use with a central remote system. Please contact your
authorized VTL dealer to set up and configure the trigger system for your amplifier.
Power On Trigger
The amplifier can be toggled between standby and power on mode using the Power Trigger.
Using a 12V trigger to power the amplifier on or off
This amplifier is equipped with a 12V (AC or DC) input that can be used to power the amplifier on or off, if
the rear AC rocker switch is in the ON position.
The connector used is a polarized Phoenix type female connector, for which males are readily available, and
which is designed to prevent shorts during connection.
Triggers are used to power on/off the amplifiers from an outside source in the system, such as the
preamplifier. Trigger outputs are typically 12 Volt systems (either AC or DC), connected via hardwired
connection between components. The trigger input on this amplifier reacts to a holding voltage: When the
MB-450 Series III Signature Monoblock Owner’s Manual
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