Fender Twin Amplifier owner manual Output Tube Bias Adjustment Instructions

CH. 1

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