Fender Twin Amp User Manual download pdf (Page 6)

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E E . V9 & V11 T ROUBLE LED* - Functional only with

the S TAND BY switch in the UP p o s i t i o n . This LED

glows re d when either the V9 or V11 tube has failed.

F F. FUSE V9 & V11 (F1)** - Protects the amplifier fro m

damage if the V 9 or V 1 1 tube were to fail. If this fuse

fails, replace the tubes in locations V 9 & V11, this fuse,

then set the BIAS and B A L A N C E.

GG. BIAS ADJUSTMENT - Trim adjustment used in

conjunction with BIAS test points to set the proper

tube BIAS.

HH. BIAS TEST POINTS - Test points used to measure

output tube BIAS.

II. BALANCE TEST POINTS - Test points used to

m e a s u re the B A L A N C E between power tube

sections.

JJ. BALANCE ADJUSTMENT - Trim adjustment used

in conjunction with the BALANCE test points to set

the proper tube BALANCE.

K K . V10 & V12 FUSE (F2)** - Protects the amplifier fro m

damage if the V 1 0 or V 1 2 tube were to fail. If this fuse

fails, replace the tubes in locations V 1 0 & V12, t h i s

fuse, then set the BIAS and B A L A N C E.

LL. V10 & V12 TROUBLE LED* - Functional only with

the S TAND BY switch in the UP p o s i t i o n . This LED

glows re d when either the V10 or V12 tube has failed.

* The TROUBLE LEDs do not indicate tube wear.

Tubes may be “worn” and sound weak even when

the TROUBLE LED still glows green. DO NOT WAIT

FOR TUBE FAILURE TO REPLACE TUBES, (see

“Tube Replacement” on the next page).

** Only replace a failed fuse with the proper type as

indicated under “Specifications” on the next page.

The fuse item F1 & F2 are used for tube failure

protection. If a fuse repeatedly fails, consult with an

authorized Fender service technician.

Visit Fender online at:

w w w . f e n d e r . c o m

w w w . m r g e a r h e a d . n e t

OUTPUT TUBE BIAS & BALANCE ADJUSTMENTS.

1. Warm up the Pro-Tube amp for 2 minutes with STAND

BY switch DOWN and OUTPUT POWER set to FULL.

Set SPEED and INTENSITY to “1“ and toggle TREMOLO

OFF. Put the STAND BY switch in the UP position.

2. Remove the bias controls cover box.

3. Set BIAS: With a DC voltmeter, measure VDC between

the “GND” and “V9,V10” test points. Adjust BIAS for .06

VDC (60mVDC).

4. Set BALANCE: With a DC voltmeter, measure VDC

between the “V9,V10” and “V11,V12” test points. Adjust

BALANCE for zero (0) VDC.

5. Replace the bias controls cover box.

IMPORTANT

1. Make BIAS and BALANCE adjustments only when

necessary. Take your Pro-Tube amp to the nearest

authorized Fender Service Center if you are not sure

about the settings.

2. Always set BIAS first, then BALANCE.

3. If the output tubes (6L6GC’s) cannot be BALANCED,

replace the output tubes (V9, V10, V11, V12), then set

BIAS and BALANCE.

BYPASS and ENGAGE Volume Levels

Use the SEND and RETURN level controls to normalize (make

equal) the ENGAGE and BYPASS volume levels. Or, set the

two levels unequal to create a preset alternate volume level,

selectable from the Footswitch. Note: The alternate volume

level will function with or without effects devices plugged into

the loop jacks.

Setting effects loop levels.

• Tu rn S E N D and RETURN knobs down to “1.”

• B Y PASS the effects loop from the rear panel or the Footswitch.

• Connect effects device(s) to the rear panel S E N D a n d

R E T U R N jacks (optional for alternate volume level setting).

• Play guitar and set the amp and instrument levels as pre f e r re d .

This is your bypass level.

• ENGAGE the effects loop.

• While playing guitar, turn S E N D and RETURN up together* to

match the bypass level set above (or to any alternate volume

level). This is your engage level.

• By quickly switching between B Y PA S S and E N G A G E w h i l e

playing, you can fine tune these settings.

*Hear unwanted distortion? Turning SEND and RETURN up at

the same rate is usually a good way of setting levels quickly

that will work with an external effects device. But with multiple

effects devices or with devices having their own level controls,

unwanted distortion may develop. Try reducing the SEND

level or the level controls on individual effects devices,

(increasing RETURN or MASTER will restore the overall

volume level). Listen for improvement after each change.

Experiment to find the right settings.

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Fender Twin Amp User Manual Page 6

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