Fender Musical Instruments Corp., 8860 E. Chaparral Road Suite 100 Scottsdale, AZ 85250
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BLUES JUNIOR
SERVICE MANUAL
NOVEMBER 1995
IMPORTANT NOTICE:
The information contained herein is CONFIDENTIAL and PROPRIETARY to Fender Musical Instruments Corp. It
is disclosed solely for use by qualified technicians for purposes of equipment maintenance and service. It is not to
be disclosed to others without the expressed permission of Fender Musical Instruments Co. All specifications
subject to change without notice.
For warranty repair service, only Fender specified part numbers are to be used. It is recommended they also be
used for post-warranty maintenance and repair.
Parts marked with an asterick (
RELIABILITY and SAFETY requirements. DO NOT USE A SUBSTITUTE!
A coded naming convention is used in the description of certain parts. The codes and what they mean are as
follows:
CAPACITOR CODES HARDWARE CODES
CAP AE=Aluminum ElectrolyticBLX=Black Oxide
CAP CA=Ceramic AxialCR=Chrome Plated
CAP CD=Ceramic DiskHWH=Hex Washer Head
CAP MPF =Metalized Polyester FilmM=Machine Screw
CAP MY=MylarNI=Nickel Plated
CAP PFF=Polyester Film/FoilOHP=Oval Head Phillips
RESISTOR CODES
RES CC=Carbon CompSMA=Sheet Metal "A" Point
RES CF=Carbon FilmSMB=Sheet Metal "B" Point
RES FP=Flame ProofSS=Stainless Steel
RES MF=Metal FilmTF=Thread Forming
RES WW=Wire WoundZI=Zinc Plated
*) indicate the required use of that specific part. This is necessary for
PB=Particle Board
PHP=Pan Head Phillips
PHPS=Pan Head Phillips Sems
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BLUES JUNIOR
SPECIFICATIONS
TypePR 295
Input impedance:1M ohm
Power output:15 Watts R.M.S. @ 5% T.H.D
Rated load impedance:8 Ohms
Speaker complimentOne 8 ohm 12" Eminence,
replica of Jenson P-10
Dimensions:
Height:16inches(41 cm)
Width:18inches(46 cm)
Depth:9-13/16 inches(25 cm)
Weight:31 lbs.(14 kg)
THEORY OF OPERATION
J1 is a high-sensitivity input with an input impedance of about 1MΩ. V1B is the first gain stage
which also contains the "FAT" switch. The FAT feature is activated by grounding the node
between bypass capacitor C3 and R9. Via the FAT switch (S1) or the optional footswitch, the
junction of R52 and R54 can be grounded. With zero volts applied to the gate of Q1, the JFET
will essentially ground C3, activating the FAT feature.
The output of V1B couples to the VOLUME control (R7). The VOLUME control is actually a
preamp overdrive control that adjusts the level of distortion. C2 attenuates high frequencies
and C1 attenuates low frequencies at high distortion settings. This takes the edge off the
distortion and prevents the speaker from flapping. V1A provides a gain of about 40, and drives
the tone control circuitry. After the tone controls, the signal is fed to V2B, which drives the
MASTER volume control (R41). From the MASTER volume, the signal splits to feed the power
amplifier and the Reverb.
U1A makes up a typical solid-state reverb drive circuit. U1B is the reverb recovery or sense
circuit, which drives the REVERB control (R51). The reverb signal is summed with the dry
signal at C6, which couples to the input of the Phase Inverter (V3).
The output tubes (6BQ5/EL84) are arranged in a push-pull configuration that will produce
fifteen (15 ) watts R.M.S. into eight (8) ohms @ 5% THD, 1kHz.
The output bias is derived from the -15Vdc supply. The voltage divider at R31 & R37
determines the bias voltage (-10.7 Vdc). C14 filters the ripple to 1mV or less.
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BLUES JUNIOR
PARTS LIST
PRINTED CIRCUIT BOARD ASSEMBLY
QTY PART # DESCRIPTION REFERENCE DESIGNATION
1049306001PCB ASSY BLUES JUNIOR ALL V(STUFFED)
1028104000BUTTON PUSH SWITCH BLACK(@ S1)
1028055REVERB UNIT 800 OHM 8EB2C1B DN(PAN)
4026577SCREW M 10-32X1 PHP BLX(SPEAKER MOUNT)
4036619SCREW M 10-32X1-1/2 THP NI(CHASSIS MOUNT)
6015990SCREW M 10-32X3/4 THP NI(BACKBOARD MOUNT)
4036618SCREW M 6-32X1-1/2 OHP BRONZ(GRILLE MOUNT)
4026419SCREW M 8-32X1 PHP STL NI(HANDLE MOUNT)
5029828SCREW PB 8X3/4 PHP ZI(REVERB PAN & CABLE CLAMP MNT)
1037617SPEAKER 12" 8 OHM 50 WATTS
1.036036343TOLEX TWEED
4022327WASHER FLAT 8X7/16 NI
MISCELLANEOUS
QTY PART # DESCRIPTION REFERENCE DESIGNATION
1049312MANUAL OWNERS BLUES JUNIOR
1049302SCHEM REDU W/SCV DIA BLS JR
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SUPPLEMENT TO:
BLUES JUNIOR
p/n 021-3105-000 (120V)
SERVICE MANUAL
Reason for supplement: Reverb improvements and improved manufacturability require changes to the PCB and to
the BOM. This supplement contains parts lists and schematics of the new circuitry. Please file it with your original
service manual.
Fender Musical Instruments Corp. 7975 North Hayden Road Scottsdale, AZ 85258
10038698001CAP CA 47pF 100VC21
10039265001CAP CA 2200pF 100VC19
10051457003CAP CD 100pF 500V 5%C3
10051458003CAP CD 470pF 500V 10%C17
10020909000CAP CD 47pF 1000V 10%C14
10020917000CAP CD 250pF 1000V 10%C5
10017620000CAP CD 1500PF 1000V 10%C9