Fender Twin Amplifier - Manual (Page 5)

L. OUTPUT BALANCE ADJUST — Used in conjunction with the BIAS
TEST POINTS (item K) to set the balance between the push/pull tube
sections of the power amp. See output Tube Bias Adjustment
Instructions below.
Output Tube Bias Adjustment Instructions —
1. Turn on the amplifier and let it warm up for at least two minutes
with the STANDBY SWITCH (item C) in the ON position and the
OUTPUT SWITCH (item D) in the OUTPUT HIGH position.
2. With a digital voltmeter set to its most sensitive DC voltage scale,
measure the voltage between the two BIAS TEST POINTS (item K)
labeled “BIAS” and adjust the OUTPUT BIAS ADJUST control (item J)
for a reading of .08 VDC (80 mVDC).
3. Connect the digital voltmeter to the two BIAS TEST POINTS (item
K) labeled “BALANCE” and adjust the OUTPUT BALANCE ADJUST
control (item L) for 0 VDC.
Notes:
1. Make bias and balance adjustments only when necessary. If you
are unsure about setting bias and balance, it is best to LEAVE THIS
FEATURE ALONE, as it is pre-set at the factory.
2. For optimum sonic performance, set bias to .08 VDC, then set bal-
ance.
3. For optimum sonic performance with increased tube life, set bias
to .06 VDC, then set balance.
4. For optimum tube life, set bias to .04 VDC, then set balance. If a
bias measurement of .04 VDC cannot be obtained, replace the
6L6GC output tubes.
5. If the output tubes can’t be balanced, check the bias setting
and/or replace the 6L6GC output tubes.
M. FOOTSWITCH JACK — Plug-in connection for the remote
footswitch. The footswitch GAIN SELECT button switches between the
Channel One Clean and Vintage Drive sounds, the CHANNEL
SELECT button switches between Channel One and Channel Two,
and the REVERB button turns the reverb on and off. Note: Any good
patch cord will work with the remote footswitch; however, a speaker
grade cord, when it’s available, is perferable to a coax guitar cord.
When the footswitch is connected, it overrides the front panel PULL
GAIN SELECT and PULL CHANNEL SELECT switches.
N. REVERB SELECT SWITCH — This three position switch assigns the
reverb to Channel One, Channel Two, or to both channels. For
example, if the switch is set to “CH. 1”, reverb will be available for
Channel One ONLY. This switch is used in conjunction with the front
panel REVERB control and the reverb on/off footswitch button.
O. EFFECTS SELECT SWITCH — This three position switch assigns the
EFFECTS RETURN JACK (item G) to Channel One, Channel Two, or
to both channels. For example, if the EFFECTS SEND and EFFECTS
RETURN jacks are being used to patch in an effect, and the EFFECTS
SELECT SWITCH is set to the “CH. 1” position, the effect will be
heard ONLY when Channel One is selected.
P. BALANCED LINE OUT — This XLR jack provides a transformer
coupled, balanced, floating ground output which can be used to
drive slave power amps, or with proper equalization, used as a send
to a mixing console for recording or sound reinforcement.
For optimum performance when driving slave amps, use high power
solid-state amplifiers of 300 watts minimum rating, and set the gain
CH. 1