Fender Blues-Junior-SM Service Manual

BLUES JUNIOR

SERVICE MANUAL

CONTENTS:

Notices

Specifications

Theory of

operation

Parts lists:

PCB assembly

Chassis assembly

Cabinet assembly

Miscellaneous

Schematics/Service diagram

Fender Musical Instruments Corp., 8860 E. Chaparral Road Suite 100 Scottsdale, AZ 85250

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 Electrolytic BLX = Black Oxide
CAP CA = Ceramic Axial CR = Chrome Plated
CAP CD = Ceramic Disk HWH = Hex Washer Head
CAP MPF = Metalized Polyester Film M = Machine Screw
CAP MY = Mylar NI = Nickel Plated
CAP PFF = Polyester Film/Foil OHP = Oval Head Phillips

RESISTOR CODES

RES CC = Carbon Comp SMA = Sheet Metal "A" Point
RES CF = Carbon Film SMB = Sheet Metal "B" Point
RES FP = Flame Proof SS = Stainless Steel
RES MF = Metal Film TF = Thread Forming
RES WW = Wire Wound ZI = 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

BLUES JUNIOR

SPECIFICATIONS

Type PR 295

Input impedance: 1M ohm

Power output: 15 Watts R.M.S. @ 5% T.H.D

Rated load impedance: 8 Ohms

Speaker compliment One 8 ohm 12" Eminence,

replica of Jenson P-10

Dimensions:

Height: 16 inches (41 cm)
Width: 18 inches (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.

BLUES JUNIOR

PARTS LIST

PRINTED CIRCUIT BOARD ASSEMBLY

QTY PART # DESCRIPTION REFERENCE DESIGNATION

1 049306001 PCB ASSY BLUES JUNIOR ALL V (STUFFED)
1 028104000 BUTTON PUSH SWITCH BLACK (@ S1)

2 047093000 CABLE 6 CKT 3.2" CJ1,3
3 029533000 CABLE JMPR 22GA 4 CKT 3.2" CJ2,4,5
1 028577000 CABLE REVERB 30" (@ P1,2,3,4)
1 038689001 CAP AE AX .47µF 100V C23
3 009512001 CAP AE AX 22µF 25V 20% C3,4,21
3 024819000 CAP AE AX 22µF 500V C10,17,18
1 041589000 CAP AE AX 47µF 500V 20% C15
1 028474000 CAP AE RDL 100µF 25V 20% C14
2 028479000 CAP AE RDL 220µF 25V 20% C29,30
2 028489000 CAP AE RDL 470µF 50V 20% C27,28
1 039255001 CAP CA 10PF 100V LL C24
1 020909000 CAP CD 47PF 1000V 10% C33
1 069724000 CAP CD 100PF 1000V10% C&F C2
1 020917000 CAP CD 250PF 1000V 10% C25
1 020867000 CAP CD 330PF 1000V 10% C20
1 017620000 CAP CD 1500PF 1000V 10% C35
1 039265001 CAP CA 2200PF 100V LL C22
2 026202000 CAP PFF .0022µF 600V C1,16
1 033581000 CAP PFF RDL .0033µF 100V 10% C26
1 033588000 CAP PFF RDL .01µF 100V 10% C31
2 024823000 CAP MPF RDL .01µF 400V 10% C6,34
1 036234000 CAP PFF RDL .015µF 100V 10% C12
4 024833000 CAP MPF RDL .022µF 400V 10% C8,9,11,13
1 024839000 CAP MPF .033µF 400V C19
2 024853000 CAP MPF RDL .1µF 250V 10% C5,7
1 024855000 CAP MPF RDL .1µF 630V 10% C32
1 049402000 CONTROL 25K B SNAPIN R29
2 034719000 CONTROL 50KB SNAP IN R41,51
1 041913000 CONTROL SNAPIN 250K 10A R8
1 040985000 CONTROL SNAPIN 250K B R28
1 049401000 CONTROL 1M 10A R7
2 064089001 DIODE 1N4003 LL CR5,7
4 026730001 DIODE 1N4006 800V LL CR1,2,3,4
2 006260001 DIODE 1N4448 SIGNAL LL CR6,12
2 029690001 DIODE HV 3KV 200MA LL CR10,11
2 009165001 DIODE ZEN 1N4744A 15V 1W 5% CR8,9

16 025802000 FSTN TAB MALE .250X.032 PCB MT CP1-13,16-18

2 031041000 FSTN TAB ML RTANG PCB .25X.032 CP14,15
2 025996000 FUSE CLIP PCB .250 & 5MM FUSE XF1
1 048827 FUSE QA 1-1/4X1/4 250V 2A F1 (100V/120V ONLY)
1 020789 FUSE QA 20mmX5mm 250V 1 AMP F1 (230/240V EXPORT ONLY)
1 016795 IC DUAL OP AMP TLO72 U1
1 030771 JACK 1/4 PCB 2/CD SCC J2 (SPEAKER JACK)
1 027674 JACK 1/4 PCB 2/CD SCC INSL J3 (FOOTSWITCH JACK)
1 037036 JACK PHONE PCB MONO CA PREMIUM J1 (INPUT JACK)

26 020888001 JUMPER WIRE 22GA .5" W1-26

1 048332 LED RED PNL MT 7" LD1
1 049305 PCB FAB BLUES JUNIOR (RAW BOARD)
1 024947001
1 024964001
5 024969001 RES CF 1/4W 5% 1.5K LL R4,11,20,23,38
1 029005001 RES CF 1/4W 5% 2K LL R49

RES CF 1/4W 5% 47Ω LL
RES CF 1/4W 5% 280Ω LL

R45
R15

BLUES JUNIOR

PRINTED CIRCUIT BOARD ASSEMBLY (CONT)

QTY PART # DESCRIPTION REFERENCE DESIGNATION

2 024977001 RES CF 1/4W 5% 4.7K LL R16,46
1 025942001 RES CF 1/4W 5% 7.5K LL R26

1 026510001 RES CF 1/4W 5% 9.1K LL R18
3 024981001 RES CF 1/4W 5% 10K LL R1,30,48
3 024987001 RES CF 1/4W 5% 22K LL R31,52,54
2 024989001 RES CF 1/4W 5% 33K LL R13,37
1 028153001 RES CF 1/4W 5% 75K LL R27
2 024997001 RES CF 1/4W 5% 100K LL R6,9
1 024998001 RES CF 1/4W 5% 120K LL R44
1 028955001 RES CF 1/4W 5% 130K LL R5
3 025059001 RES CF 1/4W 5% 220K LL R21,22,42
1 025061001 RES CF 1/4W 5% 330K LL R50
1 025828001 RES CF 1/4W 5% 430K LL R40
2 025065001 RES CF 1/4W 5% 470K LL R47,56
1 029618001 RES CF 1/4W 5% 910K LL R43
4 025069001 RES CF 1/4W 5% 1M LL R2,12,14,53
2 041741001
2 028580001
1 025829001
1 031065001 RES CF 1/2W 5% 91K LL R17
4 025116001 RES CF 1/2W 5% 100K LL R3,10,19,39
2 031067001
2 027349001 RES FILM 1W 5% 10K LL R33,55
1 041258 RES CF 2W 5% 2.2K R32
1 028091 SWITCH PUSH SLFLK SHORT STROKE S1
5 029167 TUBE SOCKET 9 PIN PCB MOUNT XV1-5
1 014689 XSTR N-CH JFET J111 TO-92 Q1

RES MOX FP 1/2W 5% 47Ω
RES MOX FP 1/2W 5% 100Ω
RES CF 1/2W 5% 150Ω LL

RES FILM 1W 5% 750Ω LL

R35,36
R24,25
R34

R57,58

CHASSIS ASSEMBLY

QTY PART # DESCRIPTION REFERENCE DESIGNATION

1 049307 CHS ASSY BLUES JUNIOR 120V (COMLETE CHASSIS)
1 047560 BRACKET TUBE RETAINER PRO. JR. (@ V4,5)

2 018022 BUSHING SNAP 5/16X17/32 BLK (@ OUTPUT TRANSFORMER)
1 026116 BUSHING SR .500X.063X7/16 BLK (@ REVERB CABLE)
1 026038 BUSHING SR. .625X.062X37/64BLK (@ POWER CABLE)
1 010401 BUSHING SR .625X.125X37/64 WHT (@ 230V & U.K. POWER CABLE)
1 026541 CABLE ASSY PWR W/.250 TAB 120V (POWER CABLE 120V ONLY)
1 048463 CABLE ASSY PWR .250 TAB 100V (POWER CABLE 100V ONLY)
1 033331 CABLE ASSY PWR 220/240V (POWER CABLE 230V ONLY)
1 038602 CABLE ASSY PWR AUST .250 TAB (PWR CABLE AUSTRALIA 240V)
1 040993 CABLE ASSY PWR 5A U.K..250 TAB (P CABLE UNITED KINGDOM 240V)
1 049101 CHS BLUES JUNIOR (RAW CHASSIS)
6 041710 KNOB POINTED PUSH ON BLK
1 027288 LENS LED RED (@ LD1)
2 016352 NUT HEX 3/8-32X3/32 TK NI (@ SPEAKER & FOOTSWITCH JACK)
9 097360 NUT HEX 4-40 EX LOCK (TUBE PCB MOUNT)
4 022004 NUT KEPS #8-32 ZINC (POWER TRANSFORMER MOUNT)
1 049102 PANEL FRONT BLUES JUNIOR (CHROME PANEL UNDER KNOBS)
1 049300 PANEL REAR BLUES JUNIOR (@ BACK OF CABINET)
9 031188 SCRW M 4-40X1/4 PHPS ZI W/WSHR (TUBE PCB TO CHASSIS MOUNT)
4 038900 SCRW TF 6-32X1/4 PHP ZI (GND LUG & OUTPUT XFMR MOUNT)
7 037353 SCRW TF 6-32X3/4 PHP ZI MAIN PCB TO CHASSIS MOUNT)
2 039371 SPRING, EXTENSION 1.81X.15" (@ V4,5)
9 038519 STANDOFF M/F 4-40 X 1/4L (TUBE PCB TO CHASSIS MOUNT)
7 047040 STANDOFF NYLON PCB SNAPIN 1/2" (PCB MOUNT)

BLUES JUNIOR

CHASSIS ASSEMBLY (CONT)

QTY PART # DESCRIPTION REFERENCE DESIGNATION

1 036570 SWITCH TOGGLE DPST W/NUTS S1 (POWER SWITCH)
3 013341 TUBE 7025/12AX7WA RUSSIAN MADE V1,2,3

2 041255 TUBE 6BQ5/EL84 V4,5
2 990430092 WASHER FLAT .482X.709 NI (@ INPUT JACK & POWER SWITCH)
2 990430010 WASHER LCK INTL 3/8X.681X.032 (@ SPEAKER & FOOTSWITCH JACK)
1 049969 XFMR OUTPUT 15W T1
1 049967 XFMR PWR BLUES JUNIOR 120V T2 (120V ONLY)
1 049968 XFMR PWR BLUES JUNIOR EXPORT T2 (100V,115V,230V,240V)

CABINET ASSEMBLY

QTY PART # DESCRIPTION REFERENCE DESIGNATION

1 049103 CAB ASSY BLUES JR TWEED (COMPLETE CABINET)
1 049103020 BACK ASSY BLUES JR TWEED (BACKBOARD)

1 038566 CABLE ASSY SPKR RT ANG 13-1/2 (SPEAKER CABLE)
1 022491 CLAMP CABLE NYL SCREW MNT 5/16

.3360 036131 CLOTH GRILLE VINTAGE TYPE

4 029821 EYELET RFLNGD .215 OD X.315 L (REVERB PAN MOUNT)
4 0415490 GLIDE PRESS-IN .75 DIA
1 049103010 GRILLE BAFFLE ASSY BLUES JR (COMPLETE GRILLE)
1 048534 HANDLE 8 3/4" LEATHER BROWN
2 036478 HANDLE CAP NI
1 041929 NAMEPLATE FENDER TWEED AMPS
4 069393 NUT 6-32 HEX EXT LOCK (GRILLE MOUNT)
4 021972 NUT T 10-32X3/4 STR 3 PRNG BLX (SPEAKER MOUNT)
4 064162 NUT T 8-32X1/2 STR 3 PRNG BLX (HANDLE MOUNT)

.0010 036650 PIN ESCUTCHEON #18X3/8 NI (NAMEPLATE MOUNT)

1 028055 REVERB UNIT 800 OHM 8EB2C1B DN (PAN)
4 026577 SCREW M 10-32X1 PHP BLX (SPEAKER MOUNT)
4 036619 SCREW M 10-32X1-1/2 THP NI (CHASSIS MOUNT)
6 015990 SCREW M 10-32X3/4 THP NI (BACKBOARD MOUNT)
4 036618 SCREW M 6-32X1-1/2 OHP BRONZ (GRILLE MOUNT)
4 026419 SCREW M 8-32X1 PHP STL NI (HANDLE MOUNT)
5 029828 SCREW PB 8X3/4 PHP ZI (REVERB PAN & CABLE CLAMP MNT)
1 037617 SPEAKER 12" 8 OHM 50 WATTS

1.036 036343 TOLEX TWEED
4 022327 WASHER FLAT 8X7/16 NI

MISCELLANEOUS

QTY PART # DESCRIPTION REFERENCE DESIGNATION

1 049312 MANUAL OWNERS BLUES JUNIOR
1 049302 SCHEM REDU W/SCV DIA BLS JR