Revv
Generator 100w
5.4
5.3
Preamp Tubes
The Generator amplifier uses 12AX7
preamp tubes in tube positions V1 V2 V3
V4 and V6. A 12AU7 preamp tube is used
in the V5 position for the FX Loop and
only a 12AU7 tube should be used in
this socket.
Preamp tubes do not need to be biased
and usually have a long life unlike power
tubes, but it is possible for a preamp
tube to become faulty at any stage of its
rated lifespan.
Power Tube Bias
The power tubes can be biased without
taking the chassis out of the wood
head shell. You will need a voltmeter or
digital multi meter set to the lowest DC
voltage range. (Make sure you refer to
the meters user manual and are famil-
iar with the meter).
Note: Use tubes that are matched! If 2
different tube types are being used, make
sure they are matched pairs. If all 4 are the
same type, make sure they are matched
pairs at the very least (and don’t mix them
up), although a matched quad is better.
To prepare:
1) Remove the rear baffle cover from
the rear of the amplifier and expose
the tubes and bias trimmers. If you are
replacing tubes, do so now with the
power off and the amplifier unplugged
from the main power receptacle. Place
the new tubes in the correct socket po-
sitions if mixing tube types. (See 5.2)
2) Next unlock the bias trimmers by
turning the nut counter clockwise and
then turn the trimmers down by turning
the trimmer shaft with a small screw-
driver in the counterclockwise direction.
If any fuses had blown, make sure to
replace them as well.
3) Now plug the amplifier in to the main
power receptacle, make sure the am-
plifier is plugged into a load or speaker
cabinet, unplug any guitar cables from
the inputs and turn on the main power.
Let the tubes warm up for one minute
4) Turn down the master volume con-
trols to zero and turn on standby to the
Revv position.
5) Verify that none of the tube fault LEDs
are on. If they are, power down the am-
plifier, remove the plug from the main
power receptacle and replace the faulty
fuse and return to step 3. If everything
checks out, move on to the next steps of
setting the bias. If it is still blowing fus-
es, a tube is at fault, try a different pair.
Set the bias:
1) Place the black lead from your meter
into the black bias test point on the am-
plifier and the red lead into the red bias
test point (The red test point on the left
is for V1 and V3 tubes, red test point on
the right is for V2 and V4 tubes).
2) Refer to the chart below for bias set
points for the tubes being used and
slowly turn the trimmer in the clockwise
direction until the value is reached.
3) Next, place the red lead into the other
red bias test point and repeat step 2 for
the other set of tubes. If 2 different pairs
of tubes are being used, refer to the
chart below and set the bias accordingly.
4) Re-check the settings of each bias
test point and make any further adjust-
ments as required.
