VAC Renaissance 70/70 - Manual (Page 8)

6
INSTALLING NEW OUTPUT TUBES
Replacement 300B output tubes should be purchased only from VAC. Output tubes are type 300B. It is
important that the tubes be checked for any tendency to mechanical or electrical shorts (see Safety Notice at
the front of this manual). It is desirable that tubes be in matched quartets for each channel, and be close to the
"bogey" values for the major parameters. Make certain that each tube fits firmly in its socket.
Refer to Figure 2 for the location and types of tubes.
ALL POWER MUST BE OFF. Remove the old tubes after they have cooled down (TUBES BECOME HOT
ENOUGH TO CAUSE SERIOUS BURNS WHEN IN OPERATION AND MAY TAKE SEVERAL MINUTES TO
COOL DOWN). Install the new tubes firmly and fully in the sockets, observing that the tube will only fit into
the socket in one orientation, as two of the pins are of larger diameter. Do not use excessive force.
A slight violet glow in the tube is not cause for concern. If at any time the plate (the outermost metal structure)
of the output tubes begins to glow bright orange or red SWITCH OFF IMMEDIATELY. The red glow indicates
that the tube is "running away", being destroyed by conducting excessive current. Tubes may run away for
several reasons:
1) The tube is not fully inserted in the socket.
2) The tube fits loosely in the socket and thus can not make correct contact. Such a tube is unusable.
3) The tube is defective.
In the event that trouble is encountered check connections and/or try another tube. Stop if the problem persists
and consult with your dealer or VAC.
Switch off immediately if any part under the gold vent grille glows orange. See Safety Notice at the front of this
manual.
For further information, refer to Tips & Advice: A Word About Tubes in General and Tips & Advice: A Word
About Output Tubes.
REPLACEMENT OF LOW LEVEL TUBES
Refer to Figure 2 for the location and types of tubes. All power must be switched off. Allow tubes to cool down.
Remove and replace with new tubes of the appropriate types, noting the location of holes in the socket and pins
of the tubes.
Replacement tubes are available from VAC and other sources.
For further information, refer to Tips & Advice: A Word About Tubes in General and Tips & Advice: A Word
About Low Level Tubes.
CARE OF CHASSIS
VAC chassis are machined aluminum for superior electromagnetic performance, and finished in durable textured
gloss paint. Cleaning with a damp cloth WHILE THE AMP IS SWITCHED OFF AND UNPLUGGED should
suffice. Do not get cleaning solutions onto or into the tube sockets.