6. Install the tube covers back to the cage by tightening the screws with a No. 2 Phillips screw driver and
following the steps below to reset the tube fault.
Resetting a Tube Red Fault
After the bad tube has been replaced, reset the fault condition using the following procedure:
1.
Turn the rocker switch off for a few seconds and then turn the rocker switch on and the Mute LED will be
blinking in red indicating the stored tube fault.
2.
Hold the Mute button for 20 seconds until the blinking red Mute LED changes to a steady green LED – This
tells the Auto Bias/Fault Sensing system that the bad tube has been replaced. Once the fault is cleared, the
amplifier will allow re-power.
3.
Before re-powering check the Plate and Screen fuses on the back of the amplifier. Using a multimeter, check
the continuity of the Plate and Screen fuses to see if they are open. If either of the fuses is open, replace it
with a good fuse of the same value and type, as indicated in the Data Sheet section of this manual.
Contact VTL or your authorized VTL dealer to purchase replacement fuses of the same type.
WARNING: If the plate or screen fuse is open, it is recommended that the amplifier be re-powered
only after waiting for at least for 5 minutes to let the power supplies drain.
MB-450 Series III Signature Monoblock Owner’s Manual
26
