Fender G-DEC-Junior-SM Service Manual

SERVICE MANUAL

G-DEC® Jr

(This is the model name for warranty claims)

p/n 2351000000 (120V)

ATTENTION:

WARRANTY SERVICE PROCEDURES

Domestic (U.S. & Canada Only): The G-DEC® Jr Amplifier is not available for warranty
field service. Any Dealer/Service Center in possession of a G-DEC
defect should contact the Fender Customer Service Support Center toll free at (866) 345­3642 or email [e-mail] to arrange for a replacement. This manual should

only be referred to for non-warranty repairs.

Non-Domestic: FMIC acknowledges that many of our International Distributors are able to
perform field or in-house warranty service on the G-DEC

®

Jr Amplifier.

Fender Musical Instruments Corporation, 8860 East Chaparral Road Suite 100 Scottsdale, AZ 85250

Issued: February, 2007

®

Jr with a warrantable

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G-DEC

(This is the model name for warranty claims)

February, 2007

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IMPORTANT NOTICE

• Copyright © 2007 FMIC. All rights reserved. All
information contained herein is CONFIDENTIAL
and PROPRIETARY and is the property of
Fender® Musical Instruments Corporation. It is
not to be sold or assigned to another party and is
disclosed solely for use by Fender Authorized
Service Centers for purposes of product service
and maintenance. All information is not to be dis­closed to others without the expressed permission
of Fender® Musical Instruments Corporation. All

specifications are subject to change without no­tice. This information and any copies produced
electronically or otherwise must be surrendered
upon demand of Fender® Musical Instruments
Corporation.

• Parts marked with two asterisks (
required use of that specific part. This is neces­sary for RELIABILITY and SAFETY requirements.

DO NOT USE A SUBSTITUTE!

**) indicate the

PARTS LIST CODES

The description codes used in the itemized Parts Lists are defined below:

CAPACITOR

CAP AE = Aluminum Electrolytic
CAP CA = Ceramic Axial
CAP CD = Ceramic Disk
CAP CR = Ceramic Radial
CAP MPF = Metalized Polyester Film
CAP MY = Mylar
CAP PFF = Polyester Film/Foil

RESISTOR

RES CC = Carbon Comp
RES CF = Carbon Film
RES FP = Flame Proof
RES MF = Metal Film
RES MOX = Metal Oxide
RES WW = Wire Wound

CODES

CODES

G-DEC

(This is the model name for warranty claims)

HARDWARE

BLX = Black Oxide
CR = Chrome Plated
HWH = Hex Washer Head
M = Machine Screw
NI = Nickel Plated
OHP = Oval Head Phillips
PB = Particle Board
PHP = Pan Head Phillips
PHPS = Pan Head Phillips Sems
SMA = Sheet Metal "A" Point
SMB = Sheet Metal "B" Point
SS = Stainless Steel
TF = Thread Forming
ZI = Zinc Plated

CODES

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3

G-DEC

(This is the model name for warranty claims)

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SPECIFICATIONS

®

Model Name: G-DEC

Release Number: PR 718

Part Numbers (120V, 60Hz) US: 2351000000
(120V, 60Hz) US DS: 2351000900
(240V, 50Hz) AUS DS: 2351030900
(230V, 50Hz) UK DS: 2351040900
(230V, 50Hz) EUR DS: 2351060900
(100V, 50/60Hz) JPN DS: 2351070900
(110V, 60Hz) TW DS: 2351010900
(220V, 50Hz) ARG DS: 2351050900
(220V, 60Hz) ROK DS: 2351090900

Power Requirement: 50W

Fuses: T 600 mA, 250V for 100V versions

T 500 mA, 250V for 120V versions
T 250 mA, 250V for 220-240V versions

Input Sensitivity: 30 mV (volume at maximum for full power, tone centered

Power Output: 15W RMS into 8 ohms @ < 5%THD, 100Hz

Impedances Input (Front/Rear): > 1M Ohm
Aux In L/R: 100 k Ohm

Speaker Complement: 8”, 8 ohm, special design (P/N 0072797000)

Dimensions Height: 12.5 in (32 cm)
Width: 13.25 in (34 cm)
Depth: 7.25 in (19 cm)

Weight: 15 lbs (6.8 kg)

Product specifications are subject to change without notice

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SERVICE NOTES

1. CHASSIS REMOVAL is accomplished by first

removing the eight (8) screws from the cabinet
back panel. The cabinet back may be removed
by gently prying it out using a flat screwdriver.
Next remove the two (2) screws from the rear
top of the cabinet into the chassis. Last remove
the two (2) handle screws at the cabinet top
that secure the chassis. Disconnect the
speaker wires form the speaker and gently slide
the chassis out from the rear.

2. MAIN PCB REMOVAL is accomplished by first

removing the eleven (11) wires at the Faston®
connectors. There are two wires at P9/P10
(BRN). A set of three (3) wires at P6/P7 (RED)
and P5 (YEL). A set of four (4) mains wires at
P3/P4 (BLK) and P1/P2 (WHT). One (1) ground
wire (GRN) at P5. Remove the two (2) Phillips
head screws that mount the small rear panel
MIDI/AUX/HEADPHONE PCB to the panel.
Remove all nine (9) knobs. Note the four (4)
knobs on the AMP SELECT, FX SELECT, KEY

5

®

G-DEC

(This is the model name for warranty claims)

SELECT and LOOP SELECT encoders are dif­ferent than the five (5) knobs on the
potentiometers. Keep them separated. Re­move the panel nut on the INPUT JACK. Pull
the small INPUT PCB down and out of the
chassis hole. Remove the nine (9) panels nuts
and nine (9) flat washers on all the controls.
Remove the two (2) screws that attach the heat
sink to the chassis. Remove the five (5) screws
and five (5) lock washers that attach the PCB to
the chassis standoffs. With the chassis facing
up drop the PCB down until the control shafts
clear the chassis and the slide it back and out
from the chassis. Note that there are two (2)
flat washers on each of the 4 encoders shafts
mentioned above, so do not lose them. To re­move the heat sink, remove the two (2) sets of
screws, shoulder washers, insulating pads, flat
washers and nuts that secure U3 and U5 to the
heat sink. Last remove the one (1) screw and
one (1) lock washer that holds the heat sink to
the PCB.

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PCB EXCHANGE POLICY

Parts marked with a single asterisk (*) in the Part
Lists are not field replaceable. If a failure due to
one of these components is detected, please con-

tact the FMIC Customer Service Department to
order the complete PCB Assembly.

CIRCUIT DESCRIPTION

This section provides concise information about new
or unusual circuitry designs incorporated into this
amplifier model. The purpose is to aid the service
technician by providing insight into the design areas
most likely to become obstacles in troubleshooting.
Information is focused for its effective use while
maintaining the security of Fender® proprietary in­formation wherever possible.

MAIN PCB - ANALOG INPUTS/OUTPUTS

Op-amp U8-B provides the high impedance instru­ment input with 15db of gain. Op-amp U8-A is a
configured as a three pole active filter. The filtered
output signal (Lin) drives the encoder portion of the
CODEC U13 of the uDSP processing section of the
amplifier. Signal VQ2 is the D.C. reference voltage
from the CODEC thus centering the output signal
about this level. Op-amp U2-B is configured as a
differential input amp recovering the signal after
uDSP processing and conversion back to an analog
signal in the decoder portion of the CODEC U13.
The LOUT+ and LOUT- signals are the input to the
differential amp which acts as a three pole active low
pass filter. The output of U2-B is applied to a unity
gain buffer amp U2-A which drives op-amp U1-A.
U1-A is a unity gain buffer when no headphone is
connected and in turn drives the power Amp I.C. U3
via R36. FET Q1 provides system muting during
power up/down in conjunction with the power sense
circuits comprised of D10, Q2, Q4.

MAIN PCB – POWER/HEADPHONE AMPLIFIER

G-DEC

(This is the model name for warranty claims)

affects the power amplifier output resistance so it re­acts with the speaker load similar to a tube amplifier.
The main internal speaker (8ohms minimum load) is
connected at P3/4. The internal speaker is discon­nected if a connection is made to the Headphone
Jack J2.

Op-Amp U1-A and U1-B act as the headphone am­plifier when a headphone is plugged into J2. The
gain of U1-A goes from unity to 21 dB when a head­phone is plugged in. U1-A drives the left side of the
headphones and U1-B drives the right side of the
headphones.

uDSP System

The uDSP system is integrated on the main PCB of
the G-DEC Jr. The UDSP system is comprised of the
microprocessor U10 (TMS320VC5501) and associ­ated memory (static RAM U14 and flash ROM U11).
Signals to and from the uDSP chip are in serial digi­tal format. Signal input is from the encoder portion of
the CODEC U13 and output to the decoder portion of
the CODEC U13. The CODEC converts the analog
input signal to digital format for processing. The
processed output digital signal and it is then con­verted back to analog format and sent to the power
amplifier.

All analog controls; LOOP Start/Stop switch; and
headphone present status are read via the analog
multiplexer U6-A. The output of the multiplexer is
read serially by the right channel of the CODEC and
sent to the uDSP system

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U3 is a 15 Watt monolithic power amp device which
drives the 8 ohm speaker. Fender conventional cur­rent feedback is applied to the power amplifier via
current sense resistor pair R24/R26 and the voltage
feedback to the amp via R28/R30. Current feedback

Note: Troubleshooting the uDSP system to com­ponent level beyond verification of power
supplies, clock, and data signals is NOT recom­mended.

MIDI System

MIDI Input signals from the external MIDI INPUT
Jack (J4) are optically isolated via U22 and sent to
the Rx line of the uDSP UART controller within U10
for processing. When MIDI is selected on the LOOP
Selector, the MIDI signal being received is passed
through to the Tx line of the uDSP UART and to the
MIDI IN of the SAM2195 Dream Synthesizer chip
U20. The SAMP2195 then plays MIDI sounds based
on the commands being sent from the external MIDI
sequence source.

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®

G-DEC

(This is the model name for warranty claims)

The +5VDC supply powers multiplexer U6, Front
Panel LED drivers Q5-Q7 and the D.C. reference
voltage string R41-R43 for the high-low reference
level for front panel potentiometers. The +5V is regu­lated down to 3.3v and 1.25V via U18 and U17
respectively. The 3.3V and 1.25 V supply power to
the uDSP system components and the MIDI I/F
components including the SAM2195 Dream Chip
U20 and U22 MIDI input opto-isolator. Reset control­ler U12 monitors the +5V supply and shuts down all
ICs in the event of power loss.

USER INTERFACE

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With internal LOOPS selected the external MIDI in­put is ignored and MIDI IN signals are generated by
the uDSP system under control of the LOOP SE­LECT and KEY SELECT controls. The rate is
controlled by the TEMPO control.

Audio output from the SAM2195 Dream Synthesizer
chip is mixed in at summing op-amp U2-B via
R50/R54. The audio output of U2-B is mixed in with
the instrument post processed (effects and amp
types added) and Auxiliary Input audio at U2-A.

POWER SUPPLIES

The power transformer secondary windings are con­nected to the main PCB at P5 through P10.

The +/-20VDC power supplies for the solid-state
power amplifier are derived from the red-yellow-red
secondary of the power transformer via full bridge
rectifiers D4/D5 and D2/D3, and main filter caps C14
and C8. The yellow center tap lead and the system’s
chassis connection are placed between these caps,
making this the system ground star.

The 4 - 16 position encoders (S2 –S5) for the LOOP,
AMP, KEY and EFFECT SELECT are read via the
port expander U9 and the data sent to the uDSP sys­tem via the I

The 4 potentiometers VOLUME(R51), GAIN(R49),
TONE(R44), and TEMPO(R31) generate DC volt­ages (+1.0V to +4.0V) that are read by the analog
multiplexer U6. IO0-IO3 are the digital control lines
used to multiplex these analog signals which are
sent serially to the system CODEC U13 on the Rin
channel. The LOOP START/STOP button and the
state of the HEADPHONE present signal are read in
a similar manner. The uDSP system reads the state
of these controls and inputs digitally from the CO­DEC.

The LOOP VOLUME is a conventional analog con­trol which accepts the MIDI left and right loop audio
signals from the SAM2195 MIDI Synthesizer via the
mixer op-amp U7-B.

2

C interface lines SCL and SDA.

The +/-12VDC power supplies for the op-amps are
regulated down from the +/-20 VDC supplies through
dropping resistors R13-14 and Zener Diodes D6 and
D7.

The +11.5VDC power supplies for the Digital circuitry
is derived from the brown-brown secondary of the
power transformer via full bridge rectifiers D15, D16,
D17 and D21 and filter caps C34. This raw supply is
then regulated down to +5VDC by U5 (7805).

®

G-DEC

(This is the model name for warranty claims)

.PARTS LIST:

QTY. PART # DESCRIPTION REFERENCE DESIGNATION

1 REF *PCB ASSY G-DEC® Jr MAIN COMPLETE PCB ASSY

FIELD SERVICE ON THIS ASSY. LIMITED TO THE PART NUMBERS LISTED BELOW

5 REF WASHER TOOTHED AW-3 PCB MOUNTING
2 0072781000 JACK DIN PIN J4 MIDI IN
5 REF CONTROL 10kB R3,R31,R38,R44,R49,R51
4 0055983000 ENCODER 16PS 4BITGRY RTRY S2-S5
1 0041812000 IC REGULATOR +5V MC7805CT U5
1 0051934000 IC POWER AMP TDA2050V 32W U3
1 REF *HEAT SINK G-DEC® Jr @ U3, U5
2 REF SCREW M3X10 BLK B/H @ U3, U5
2 REF WASHER FLAT M3 @ U3, U5
2 REF NUT M3 NIP @ U3, U5
2 REF WASHER SPLIT LOCK M3 @ U3, U5
2 REF BUSHING PATR-2935 @ U3, U5
2 REF SILICONE PAD TO-220 @ U3, U5
4 0051658000 JACK MONO 1/4" J3 INPUT
2 0072780000 JACK 3.5 mm STEREO W/SWITCH J1, J2 AUX INPUT, HEADPHONE OUTPUT

PART S LIST:

QTY. PART # DESCRIPTION REFERENCE DESIGNATION

1

REF CHASSIS G-DEC Jr

1 REF *PCB ASSY G-DEC Jr MAIN COMPLETE PCB ASSY
1

REF **XFMR G-DEC® Jr 120V

-

REF **XFMR G-DEC® Jr 230V

-

REF **XFMR G-DEC® Jr 100V

1

0039287000 POWER SWITCH SNAP IN

1

REF TRANSFORMER GASKET @ TRANSFORMER BASE

4

006470600 KNOB ROTARY G-DEC® Jr @ POTS (with flat washer and nut)

5

REF

1

0048451000

8

REF

1 0072791000 **IEC INLET AC INLET

-

0048381000

1

0003111000 **FUSE T500mA 5X20MM 120V UNITS ONLY Littelfuse 218P.500

-

REF **FUSE T250mA 5X20MM 230-240V UNITS ONLY Littelfuse 218P.250

5

REF

5

REF

3

REF

2

REF

2

REF

3

REF

KNOB ENCODER G-DEC® Jr
PUSH BUTTON IVORY
WASHER DIA 9 CRP

**FUSE T600mA 5X20MM

M3X5 ZNP B/H
AW-3
FLANGE NUT M) 4 ZNP

TF 6-32X6 BLK B/H
T 2.1X8 BLK R/H

TF 4-40X6 ZNP B/H

MAIN – PCB ASSEMBLY

CHASSIS ASSEMBLY

FX, KEY, AMP, LOOP (with flat washer and nut)
LOOP START/STOP
2EA @ INSIDE OF ENCODER SHAFTS

100V UNITS ONLY Littelfuse 218P.600

@ PCB
@ PCB
@ XFMR, GND

@ REAR I/O PCB
@ MIDI JACK
@ HEAT SINK

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* Non-serviceable part. Replace complete parent assembly. See PCB EXCHANGE POLICY section above.

shaded Unique Fender® part. Order directly from the FMIC Parts Department.
shaded + * Access to this part or assembly is controlled. Please contact the FMIC Customer Service Department.

** Safety Requirement part. Replacement must match Safety Agency…–Value, if specified –Type, if specified –Approval Mark(s) if on part.

shaded + ** Both a unique Fender® part and a Safety Requirement part as defined above.

Y

®

G-DEC

(This is the model name for warranty claims)

PART S LIST:

QTY. PART # DESCRIPTION REFERENCE DESIGNATION

1 REF *CABINET ASSY G-DEC® Jr
5 REF SCREW M) 4X30 BLK T/H @ CABINET BACK
1 REF SPEAKER 8" 8 OHM G-DEC® Jr
4 REF NUT FLANGE M) 4 ZNP @ SPEAKER
1 0047248000 **CORD PWR W/IEC CONN DOM 120V ONLY

- 0047249000 **CORD PWR W/IEC CONN 230V UK 230V UK ONLY

- 0047250000 **CORD PWR W/IEC CONN 240V 240V AUS ONLY

- 0047251000 **CORD PWR W/IEC CONN 230V 230V EUR ONLY
0057674000 **CORD PWR W/IEC CONN 230V ARG 230V ARG ONLY

-

0053997000
1 0072802000 *BADGE G-DEC®
2 REF SCREW T) 2.1X10 NIP R/H @ BADGE
1 0051043000 *NAMEPLATE FENDER GENERIC
4 0036500000 ESCUTCEHON PINS @ NAMEPLATE
1 REF MANUAL OWNERS G-DEC® Jr
5 REF SCREW NO. 8 U32X30 BLK O/H @ CHASSIS TOP AND REAR
3 REF SCREW M 3.5X10 BLK T/H @ CHASSIS REAR
4 REF WASHER BLK FINISHING TYPE @ CHASSIS
1 0037121000 HANDLE RIBBED 9 1/4"
2 0032524000 HANDLE STRAP METAL INSERT
2 0025395000 HANDLE CAPS - NICKEL
2 REF M)4X32 NIP O/H @HANDLE
4 REF FOOT RUBBER 18X10
4 REF T)2.1X8 BLK R/H @ FEET

**CORD PWR W/IEC CONN 100V JPN

END ITEM ASSEMBL

100V JPN ONLY

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* Non-serviceable part. Replace complete parent assembly. See PCB EXCHANGE POLICY section above.

shaded Unique Fender® part. Order directly from the FMIC Parts Department.
shaded + * Access to this part or assembly is controlled. Please contact the FMIC Customer Service Department.

** Safety Requirement part. Replacement must match Safety Agency…–Value, if specified –Type, if specified –Approval Mark(s) if on part.

shaded + ** Both a unique Fender® part and a Safety Requirement part as defined above.

10

G-DEC

(This is the model name for warranty claims)

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Service Diagram List

Service Diagram (Schematic) ............G-DEC® Jr PCB