V6-V7
Power amp tubes--for best operation, all power tubes should be changed at the same
time. Use a matched pair if at all possible.
Checking for microphonic tubes
As tubes wear, some problems can come up. One of the most common symptoms is a
ringing sound. This is usually due to the tube becoming microphonic (like its name
suggests, it's picking up sound and amplifying it).
With the amp unplugged and cooled off, examine the tubes to make sure they're in tight
and straight. Never twist them! Gently grasp the tube and wiggle it into place. Because
some of the tubes are inside of metal sleeves, you will have to remove the sleeves to check
them for microphonics. Grasp the sleeve with your fingers and depress it (it's spring-
loaded) and turn to the left (counterclockwise). Now pull it off; this may require a little
wiggling action.
Preamp tube first aid
If you hear ringing (a feedback-like high-pitched sound) in your amp, it's probably coming
from a Preamp tube. Here's a procedure to find which tube is giving you trouble.
With nothing plugged into either the High Gain or Low Gain inputs, and the Master
controls turned down to 5 or below, turn the amp on.
Turn up the Volume on Channel 1, or Channel 2. Now use the tip of a pencil to gently tap
the end of each of the small tubes (V1 through V5) and listen for sustained ringing. Turn up
the Volume and Master knobs and keep tapping until you find the tube that rings (or
squeals).
Turn off the amp, and allow the tubes to cool. Now pull out the troublesome tube and
replace it with one of the same value (that is, if you're pulling out a 12AX7, replace it with
a 12AX7).
Make sure that the tube is oriented correctly when pulling it out or putting it back in. If you
look at the end of the tube and the socket, you'll notice that the nine pins are arranged in an
incomplete circle. Always make sure the pins are aligned correctly. Never force a tube into
its socket.
Remember to put the sleeve back on after you check or replace a tube.
Power amp tube first aid
Like Preamp tubes, power amp tubes can go bad or wear out. Your Venus 6 has four power
amp tubes, and if one goes bad, they should all be replaced. This assures optimum output
and tone.
If a power tube shorts out, the HT Fuse will be blown. Remove power from the amp and
replace the fuse before doing the following:
