Fender Super Bassman Instrucciones De Funcionamiento página 4

Many musicians desire the rich
and full tones produced by a
tube amplifier, but heavy amps
full of glass tubes which must
be maintained and occasionally
serviced can be intimidating.
The goal of Automatic Bias is to
maximize tube life and ensure
peak performance.
Bias: What is it? Why is it Important?
The bias setting on your tube power amplifier determines the idle
current flowing through each tube. In other words, the bias setting
(WARM/NORMAL/COOL), determines how much power is flowing
through each tube at idle (while the amplifier is not being played).
Tubes are complex devices that are difficult to manufacture in a
consistent way. To account for this, tubes are often measured and
then given "grades" to sort them by performance characteristics. All
tubes of the same grade can be set at the same bias, which is why
in traditional tube amplifiers (without Fender Automatic Bias) it is
necessary to replace all output tubes at the same time and with a
matched set of the same grade. Furthermore, if the new matched
set is not the same grade as the old matched set the amplifier would
need to be taken to a service center to have the bias adjusted.
Fender Automatic Bias monitors the bias of each tube individually.
If one tube fails, it is not necessary to replace all output tubes with a
matched set. Simply replace the single failed tube with a tube of the
same type and grade. When it is necessary or desired to replace all six
(6550C) output tubes at the same time, a matched set (of six tubes) of
any grade may be used.
The bias setting affects amplifier tone, dynamics, tube life, and power
consumption in the following ways:
WARM: More aggressive (dirtier) tone, faster attack. Shorter tube
life, higher power consumption.
NORMAL: Typical setting. Good balance between tone and tube
life.
COOL: Less aggressive (cleaner) tone, smoother attack. Longer
tube life, lower power consumption.
Adjusting the Tube Bias
Press the up/down ADJUST buttons for WARM/COOL settings. Each
button may be pressed 5 times from the NORMAL setting for the
full range of bias adjustment. The range of bias (per tube) is 23mA
(COOL) to 28mA (NORMAL) to 33mA (WARM). The amplifier does not
need to be in standby for this adjustment. Allow 10-20 seconds for
the adjustment to be completed. The LEDs will stop blinking when
the adjustment is complete.
NOTE: To preserve the amplifier's rich tube tone, Fender Automatic
Bias will not make any bias adjustments while the amplifier is being
played. Fender Automatic Bias will always wait until the amplifier
is at idle or being played at very low levels before making any
adjustments.
Press and hold both the up and down arrows to restore the bias to
factory settings (NORMAL). Always restore the bias settings to factory
setting after installing an entire set of new tubes with a different
grade than the previous set.
Fender Automatic Bias
AUTOMATIC BIAS
WARM
ADJUST
NORMAL
1A 1B 2A 2B 3A 3B
COOL
OUTPUT TUBE STATUS
PATENT PENDING
Output Tube Status LED Indicators
Fender Automatic Bias has one LED indicator for each output tube,
corresponding to the location of each output tube from left to right
on the back of the amplifier. These LEDs show the current status of
the output tubes and can aid in service and trouble-shooting. Here is
a definition of each of the LED display functions:
GREEN LED mov- The tubes are warming up. You should always wait longer
ing left to right than one minute before taking the amplifier out of STANDBY.
The SPEAKER OUTPUT switch must be ON or the amplifier will
remain in the warmup state.
NOTE: If the STANDBY switch is set to ON before one minute
(not recommended), the display will not update until after the
one minute warm up period has passed.
LED is solid green
The tube is OK and operating at the desired bias level (WARM/
NORMAL/COOL).
LED is green and
The bias for that tube is being adjusted. It can take up to 20
blinking seconds to complete the adjustment.
NOTE: If an LED blinks continuously for longer than 5 minutes
(after power-up or bias adjustments), that tube is worn out and
should be replaced.
LED is orange The tube is wearing out and should be replaced with a new tube
with the same tube rating.
Within any pair
The tube indicated with the red LED has failed, and should
(1A/1B, 2A/2B, be replaced (refer to the Tube Replacement section on next
3A/3B) one LED is page for instructions). The tube indicated with the orange LED,
red and the other has been shut off to allow the amplifier to run safely with the
remaining pair(s) of tubes (green LEDs).
LED is orange
NOTE: In this condition the amplifier will continue to operate
safely (and allow you to finish your gig), but will operate with
only the remaining power tubes at reduced power.
Within any pair Sometimes, if a tube fails under certain high level signal condi-
(1A/1B, 2A/2B, tions, Fender Automatic Bias cannot determine which tube of
the pair has failed, and displays both in the pair red. It is still
3A/3B) both LEDs
safe to operate the amplifier in this mode, but it will operate at
are red
reduced power (as discussed above).
There are two service options in this situation (refer to the Tube
Replacement section for tube replacement procedure):
1. Replace both tubes that were indicated red, and the appro-
priate fuse (BB).
OR
2. Troubleshoot to replace only the failed tube. This is the best
option if replacing both tubes is not practical (i.e., at a gig),
and spare fuses are available.
A. Replace either of the tubes that were indicated red, with
a new or known good tube. Keep the removed tube
handy, in case it was not actually the failed tube.
B. Replace the appropriate tube fuse (BB) with the same
type and rating.
C. Turn POWER (M) on, keep the amplifier in STANDBY (N) at
least one minute.
D. Take the amplifier out of STANDBY, wait 10-15 seconds
for Fender Automatic Bias to determine the tube status
and update the display.
E. If all LEDs are now green, the bad tube was replaced (dis-
pose of the removed tube properly).
F. If the two LEDs remain red, the wrong tube was replaced.
Keep the removed tube and proceed to step G.
G. Remove the other tube in the pair with the red LED
indicator and replace it with the tube that was removed
during step A. Repeat steps B-E.
H. If there are still two red LEDs, both tubes had failed.
Replace the tube from step g with a brand-new tube (dis-
pose of the removed tube properly). Repeat steps B-E.
All LEDs are red
Multiple tube failures; the amplifier will be silent. Service each
or orange pair of tubes as described above. This is unlikely to occur.
NOTE: If any tubes are missing (not installed), the LED indica-
tor for that tube will display orange. A pair of tubes may also
display orange if the fuse for that pair of tubes is missing and
Fender Automatic Bias did not detect a tube failure.
All LEDs flash at a The amplifier has been placed in STANDBY (N) or the SPEAKER
slow rate OUTPUT switch (Q) has been set to MUTE.
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