VAC Renaissance 30/70 - Manual (Page 2)

IMPORTANT UPDATE
PLEASE READ CAREFULLY
Your Renaissance Thirty/Seventy has been fitted with the “300B Sentry” thermal sensor
circuit. It works in conjunction with the indicator lights located between the output tubes,
and has two functions:
1) If the idle current in a 300B output tube should drop well below acceptable limits, the
light adjacent to that tube will light green. The tube should be replaced.
These lights will also be green when the amplifier is first switched on, and will
extinguish when the bias resistors have reached normal operating temperature after
several minutes. Note: a strong cool air current could cause the lights to remain green
even in normal operation.
2) Should any output tube draw excessive idle current (run away or internal short)
the light adjacent to that tube will glow red and the high voltage supply within
the amplifier will be shut down. The red light will stay on until the power switch
is turned off. This tube must be replaced.
The lights for the other three tubes will show green after a few minutes...this should
be disregarded.
This protection feature normally will operate with much greater speed than the AC
line fuse, and provides a high degree of protection against elevated temperature or fire
due to a major failure in an output tube. However, completely failsafe methods are not
possible. As with any high power electrical device, never leave the amplifier run
unattended. Turn the amplifier off immediately if you smell any strong odor, or if you
see any parts glowing orange through the gold vent grille.
To minimize difficulties, always source the highest quality tubes, avoiding inexpensive or
generic 300B tubes. For best sound we recommend obtaining replacement tubes from VAC,
stating that they are for use in the Renaissance Thirty/Seventy.