Fender G-DEC 30 User manual

G-DEC®30
(This is the model name for warranty claims)
p/n 2350500000 (120V)
SERVICE MANUAL
ATTENTION:
WARRANTY SERVICE PROCEDURES
Domestic (U.S. & Canada Only): The G-Dec 30 Amplifier is not available for warranty field
service. Any Dealer/Service Center in possession of a G-Dec 30 with a warrantable defect
should contact the Fender Customer Service Support Center toll free at [phone] or
email [e-mail] to arrange for a replacement. This manual should only be re-
ferred 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 30 Amplifier.
Fender Musical Instruments Corporation, 8860 East Chaparral Road Suite 100 Scottsdale, AZ 85250
Issued: December, 2006

G-DEC®30
(This is the model name for warranty claims)
2
December, 2006
IMPORTANT NOTICE
•Copyright © 2006 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 dis-
closed to others without the expressed permission
of Fender® Musical Instruments Corporation. All
specifications are subject to change without no-
tice. This information and any copies produced
electronically or otherwise must be surrendered
upon demand of Fender® Musical Instruments
Corporation.
•Parts marked with two asterisks (**) indicate the
required use of that specific part. This is neces-
sary for RELIABILITY and SAFETY requirements.
DO NOT USE A SUBSTITUTE!
PARTS LIST CODES
The description codes used in the itemized Parts Lists are defined below:
CAPACITOR CODES
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 CODES
RES CC = Carbon Comp
RES CF = Carbon Film
RES FP = Flame Proof
RES MF = Metal Film
RES MOX = Metal Oxide
RES WW = Wire Wound
HARDWARE CODES
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

G-DEC®30
(This is the model name for warranty claims)
3
SPECIFICATIONS
Model Name: G-DEC®30
Release Number: PR 695
Part Numbers (120V, 60Hz) US: 2350500000
(240V, 50Hz) AUS: 2350503900
(230V, 50Hz) UK: 2350504900
(230V, 50Hz) EUR: 2350506900
(100V, 50/60Hz) JPN: 2350507900
Power Requirement: 75W
Fuses: F1A, 250V for 100-120V versions
F500mA, 250V for 230-240V versions
Power Output: 30W (15.5Vrms) into 8 ohms @ < 5%THD, 100Hz
Impedances Input (Front/Rear): 1M Ohm
Aux In L/R: 2.5k Ohm
Speaker Complement: 10”, 8 ohm, special design (P/N 0072797000)
Dimensions Height: 15.5 in (40 cm)
Width: 16.75 in (43 cm)
Depth: 8.125 in (21 cm)
Weight: 21 lbs (9.6 kg)
Product specifications are subject to change without notice

G-DEC®30
(This is the model name for warranty claims)
4
SERVICE NOTES
1.
2.
3.
CHASSIS REMOVAL is accomplished by first
removing the five (5) screws from the cabinet
back panel. The cab back may be removed by
gently prying it out using a flat screwdriver.
Next remove the three (3) screws from the back
of the chassis into the top of the cabinet. Last
remove the four (4) chassis screws at the cabi-
net top that secure the chassis. Disconnect the
speaker wires form the speaker and gently slide
the chassis out from the rear.
DSP PCB REMOVAL is accomplished by re-
moving the three (3) screws that secure the
DSP PCB to the main board. Carefully remove
the two (2) ribbon cables to the keypad PCB
and LCD at P24A and P71. Gently lift the DSP
PCB up and disconnecting it from the header
on the main board.
MAIN PCB REMOVAL is accomplished by first
removing the two (2) nuts from the front panel
jacks. Next remove the three (3) knobs and
then removing the nuts and washers at the
pots. Then remove the two (2) PCB mounting
screws. Disconnect all ribbon cables (P6A,
P9A, P10A), transformer wire connector (P5),
and unplug the speaker wire faston connectors
at P1-P2. Last remove the two (2) screws,
nuts, and washers from the main heatsink at
the chassis bottom. If the DSP PCB is still con-
nected, remove the two (2) ribbon cables from
the keypad PCB and LCD at P24A and P71.
Gently slide the PCB back enough for the jacks
and pots to clear the chassis holes. It is rec-
ommended that as much troubleshooting
and rework as possible be performed with
this PCB installed in the chassis with the
DSP PCB connected.
4.
5.
REAR PCB(S) REMOVAL is accomplished by
removing all nuts and screws at the jacks. Dis-
connect the ribbon cables from the headers
(P6B, P9B, P10B) and unplug the black/white
wires from P1-P2 on the main board.
KEYPAD PCB REMOVAL is accomplished by
first removing all the ribbon cables at the DSP
PCB (P24A, P71). Next remove the four (4)
screws holding the plastic faceplate to the
chassis. Then remove the five (5) screws secur-
ing the PCB. Remove the grey data wheel and
the nut/washer at the encoder. Disconnect the
wire connector at P11. The PCB may now be
removed from the faceplate.
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.

G-DEC®30
(This is the model name for warranty claims)
5
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 in-
formation wherever possible.
Note: Troubleshooting to component level on
the Main and Keypad PCBs is best accomplished
in Self-Test Mode (pass thru screen). Refer to
Self-Test Procedure found after DSP PCB. All
test points found on the service diagram are lo-
cated on the Main PCB top for easy access.
MAIN PCB - ANALOG INPUTS/OUTPUTS
Op-amps U1A-B provide high impedance inputs to
the front and rear instrument inputs with 12db of in-
put gain. Op-amps U3A-B comprise differential
amps (unity gain) for increased noise immunity. Op-
amps U4A-B provide differential inputs with 12dB of
gain to the Aux In L&R signals. Buffer amplifiers
U50A-B, U51A-B, U12A-B, and U53A-B provide dif-
ferential inputs to the ADCs U11 and U21. These
stages attenuate 15dB to compensate the for the full
scale input voltage of the ADCs. These inputs are
biased to +2.51VDC reference voltage from the VQ
pins on U11 and U21.
Op-amps U52A-B act as a differential reconstruction
filter (anti-aliasing) for the main (instrument, aux in,
MIDI) stereo output signals received from DAC U6,
and stereo Line Out signals from DAC U30.
Op-amps U24A-B and followers U14A-B provide
12dB of gain and sufficient current capability to drive
the stereo Phones jack.
MAIN PCB - POWER AMPLIFIER
Input signal is applied to the power amp at C120.
The power amplifier U10 (LM3886) is provided nega-
tive current feedback from sense resistor R119
through C92 and R112. DC feedback is provided by
network R102, R108, and C92. Current feedback
affects the power amplifier output resistance so it re-
acts 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 discon-
nected if a connection is made to the External
Speaker Out jack J8.
MAIN PCB - POWER IC BIAS/MUTE PIN
Power IC U10 (LM3886) has a bias/mute pin which
requires >1mA of current for the amplifier to come
out of mute. When AC power is first applied, the
base of Q11 is held at -31VDC keeping Q11 off and
preventing current flow from bias pin U10.8. The
power amplifier remains muted until C118 charges to
a voltage above zener D11 (10V) and Q11 Vbe (ap-
proximately -21VDC) and Q11 turns on allowing
current to flow.
If nothing is plugged into the Phones jack, R48 is
held at ground turning on PNP transistor Q8. With
Q8 on, the collector of Q8 is at +5VDC driving the
base of Q6 to above -5.5VDC. Zener D10 clamps
the emitter of Q6 to -6VDC. With the base of Q6
above -6VDC, Q6 turns on allowing current to flow
from bias pin U10.8 bringing the amplifier out of
mute. If headphones (or other ¼” plug) are con-
nected to the Phones jack, R48 is lifted from ground
turning off Q8. This forces the base of Q6 to below
-6VDC shuting it off and preventing current from
flowing from bias pin U10.8 muting the amplifier.
The current through Q11 is now shunted from D10.

G-DEC®30
(This is the model name for warranty claims)
6
DSP PCB
The DSP PCB is connected to the main PCB via 30
pin header U24 for all power supply, master clock
and I/O data signals. It also connects to the keypad
PCB via connector at P24A for signals to read the
front panel buttons, read the 16-position rotary en-
coder, and drive the front panel LEDs and LCD
backlight. The LCD display is connected via the rib-
bon cable at P71. The DSP PCB contains the
microprocessor (uPC) U5 (DSPB56367) and associ-
ated memory (static RAM U7-9, flash ROM U16).
Note: Troubleshooting this PCB to component
level beyond verification of power supplies,
clock, and data signals is NOT recommended.
Use Self-Test Mode to test all controls and DSP
functions.
Self-Test Mode Procedure:
1. Apply power to unit while holding
Song/Tuner and Amp buttons.
2. Follow on-screen directions. In the event of
errors, messages will be displayed on the
screen. Press Exit to skip to next test.
3. After passing all self tests, at pass thru
screen (last test) set Gn=0.5 (use Data
Wheel) to verify test point voltages on ser-
vice diagram.
KEYPAD PCB
The Keypad PCB is a breakaway from the Main PCB
and is home to the front panel buttons (S1, S3, S5-
14), front panel LEDs (D2-3, D41-49, D51-52), and
the Data Wheel (16-position rotary encoder S2). The
LCD backlight is connected to at P11.
POWER SUPPLIES
The power transformer (PT) secondaries are con-
nected to the main PCB at connector P5.
The +/-31VDC power supplies for the solid-state
power are derived from the red secondary of the
power transformer via full bridge rectifiers D15-16,
D27-28, and main filter caps C129-130. This yellow
center tap lead and the system’s chassis connection
are placed between these caps, making this the sys-
tem ground star.
The +/-12VDC power supplies for the op-amps are
regulated down from the +/-31VDC supplies through
dropping resistors R129-130 and regulators U27
(7812) and U28 (7912).
The +/-5VDC power supplies for the Digital circuitry,
front panel LEDs, and LCD backlight are derived
from the blue secondary of the power transformer via
full bridge rectifiers D59-62 and filter caps C131-132.
These raw supplies are then regulated down to +/-
5VDC by regulators U20 (7805) and U25 (7905). The
center tap (yellow lead mentioned above) is inter-
nally connected inside the transformer and is
common to all supplies.
The +5VDC supply powers ADCs U11 and U21,
DACs U6 and U30, MIDI IN/OUT circuitry, and is
regulated down to +2.5VDC (regulator U23) for the
Dream Chip U2 and +3.3VDC (regulator U32) for the
microprocessor U5 (DSPB56367) and all other
chips/memory on both the Main and DSP PCBs.
Reset controller U13 monitors the +5V supply and
shuts down all ICs in the event of power loss.
The -5VDC supply powers the front panel LEDs and
the LCD backlight.

G-DEC®30
(This is the model name for warranty claims)
7
MIDI INTERFACE
MIDI In/Out signals are connected to the main DSP
through P6A-B and processed by an auxiliary uPC
(U17) and MIDI Synthesizer Chip (U2). MIDI In sig-
nals are buffered by opto-isolator U22 and translated
to +3.3V logic. MIDI Out signals are buffered by
transistor pair Q4-5 which translates to +5V logic.
Note: General MIDI functionality (pass thru) can be
tested in Self-Test Mode. Software/firmware updates
can be downloaded via MIDI connection to a PC /
MAC using Updater utility available from
www.fender.com.
USER INTERFACE
Button operation is created by contacts on the back-
side of the elastomeric keypad shorting to adjacent
pads on the keypad PCB when pressed.
The Data Wheel (16 position rotary encoder S2) pro-
duces 4 bits of data that is processed directly by the
uPC. All user interface buttons and the red/green
LED status of the Save (D3 and D51), Song/Tuner
(D4 and D52), and Start-Stop (D2) buttons are also
directly controlled by the uPC.
The 3 potentiometers (Volume VR60, Guitar Tone
VR2, and Backing Level VR1) generate DC voltages
(+3.3V to 0V) that are read by A/D inputs (pins 2-4)
on the auxiliary uPC (U17) for processing by the
uPC.
FOOTSWITCH
The optional ULT-4 footswitch is connected at the
Footswitch jack J5 with a standard 2 conductor ca-
ble. The ULT-4 footswitch has an internal uPC
which directly communicates with pins 5, 7, and 26
of the auxiliary uPC (U17) on the main PCB to
handle all switching and tuner functions.

G-DEC®30
(This is the model name for warranty claims)
8
.PARTS LIST: MAIN – PCB ASSEMBLY
QTY. PART # DESCRIPTION REFERENCE DESIGNATION
1 0072798000 *PCB ASSY G-DEC 30 MAIN COMPLETE PCB ASSY
FIELD SERVICE ON THIS ASSY. LIMITED TO THE PART NUMBERS LISTED BELOW
2 0072781000 JACK DIN 5 B/GDEC 30 J9-10 MIDI IN, MIDI OUT
3 0062770000 CONTROL SNAPIN 10k2B W/ DTNT RUMBLE VR1-2, VR6 BACKING LVL, GTR TONE, VOL
1 0072778000 ENCODER 16PS 4BITGRY RTRY B/GDEC 30 S2 DATA WHEEL
1 0066396000 IC POWER AMP 56W/MUTE LM3886 U10
1 0072801000 *HEATSINK G-DEC 30 @ U10
1 REF SCREW M) 3X10 BLK B/H @ U10
1 REF NUT M) 3 NIP @ U10
1 REF WASHER LOCK DIA 3.0 @ U10
1 REF BUSHING PATR-2935 @ U10
1 REF MICA PAD MULTIWATT-15 @ U10
4 0072789000 JACK MONO 1/4" B/GDEC 30 J1 J2 J5 J8 INPUT (F/R), FTSW, EXT SPKR
1 0072780000 JACK RCA DUAL B/GDEC 30 J3 AUX IN
2 0070924000 JACK STEREO 1/4" B/GDEC 30 J6 J7 LINE OUT (RT, LFT)
1 0072790000 JACK STEREO 1/4" HP B/GDEC 30 J4 PHONES
PARTS LIST: DSP – PCB ASSEMBLY
QTY. PART # DESCRIPTION REFERENCE DESIGNATION
1 0069345000 *PCB ASSY DEC 30 DSP COMPLETE PCB ASSEMBLY
PARTS LIST: CHASSIS ASSEMBLY
QTY. PART # DESCRIPTION REFERENCE DESIGNATION
1 REF CHASSIS G-DEC 30
1 REF PANEL FRONT B-DEC 30
1 REF PANEL REAR B-DEC 30
1 0053860000 **CAP MPF .1uF 250VAC 20% @ AC INLET
1 0072813000 **XFMR B/GDEC 30 120V
- 0072814000 **XFMR B/GDEC 30 230V
- 0072815000 **XFMR B/GDEC 30 100V
3 0072851000 KNOB ROTARY G-DEC 30 @ POTS
1 0072779000 KNOB ENCODER B/GDEC 30 DATA WHEEL
1 0069960000 **SWITCH RUMBLE SERIES POWER SWITCH
1 0072791000 **IEC INLET W/ FUSE B/GDEC 30 AC INLET
2 REF SCREW M) 3X8 BLK F/H @ AC INLET
1 0048381000 **FUSE F1A 5X20MM 100-120V UNITS ONLY
- 0048377000 **FUSE F500mA 5X20MM 230-240V UNITS ONLY
3 REF FERRITE CORE HF70 SH 35X1.3X12 @ RIBBON CABLES TO DSP PCB
1 REF BUSHING 3N-4P @ SPKR WIRES
3 REF STANDOFF M 2.6X11.5L @ DSP PCB
6 REF SCREW M) 2.6X6 ZNP B/H @ DSP STANDOFFS
3 REF SCREW M) 4X10 ZNP T/H @ XFMR, GND
3 REF FLANGE NUT M) 4 ZNP @ XFMR, GND
2 REF SCREW M) 3X10 BLK B/H @ HEATSINK
4 REF NUT M) 3 NIP @ HEATSINK / AC INLET
*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.

G-DEC®30
(This is the model name for warranty claims)
9
PARTS LIST: CHASSIS ASSEMBLY
QTY. PART # DESCRIPTION REFERENCE DESIGNATION
2 REF WASHER LOCK DIA 3.0 @ HEATSINK
6 REF SCREW TF) 4-40X6 ZNP B/H @ FACEPLATE / MAIN PCB
1 0072784000 *FACEPLATE B/GDEC 30
1 REF WINDOW ACRL 59X38X1.0 T @ FACEPLATE
1 0072786000 *KEYPAD B/GDEC 30 @ FACEPLATE
1 0072785000 *LCD MODULE B/GDEC 30 @ FACEPLATE
4 REF SCREW T) 1.6X4 BLK R/H-#2 @ LCD MODULE
5 REF SCREW T) 2X6 BLK R/H @ FACEPLATE / KEYPAD PCB
1 REF CABLE RIBBON 5 CKT @ P9A-P9B
2 REF CABLE RIBBON 6 CKT @ P6A-P6B, P10A-P10B
1 REF CABLE FLEX FLAT 20 CKT @ P24A-P24B
1 REF SCREW T) 3X10 BLK P/H-#2 @ RCA JACK
4 REF SCREW T) 2.1X8 BLK R/H @ MIDI JACKS
3 REF WASHER TOOTH AW-3 @ AC INLET / DSP PCB
PARTS LIST: CABINET ASSEMBLY
QTY. PART # DESCRIPTION REFERENCE DESIGNATION
1 0072800000 *CABINET ASSY G-DEC 30 COMPLETE CABINET
4 0029071000 CORNER 2 HOLE NI @ CAB REAR
2 0026566000 CORNER 2 HOLE W/HOOK @ CAB FRONT BTM
8 REF SCREW T) 3.5X10 NIP T/H-#1 @ CORNERS
1 0062774000 HANDLE RUMBLE 60/100 W/ INSERT
2 0072792000 BRACKET HANDLE GDEC 30 @ HANDLE
2 REF SCREW M) 4X30 NIP O/H @ HANDLE
7 REF NUT T M4 @ CAB BACK / HANDLE
4 REF STUD BOLT M) 4X35L BLK @ BAFFLE (SPEAKER)
4 REF SCREW T) 3.5X30 BLK T/H-#1 @ BAFFLE CLEATS
4 0072803000 FOOT RUBBER 18X10
4 REF SCREW T) 3.5X15 BLK T/H-#1 @ FEET
*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.

G-DEC®30
(This is the model name for warranty claims)
10
PARTS LIST: END ITEM ASSEMBL
Y
QTY. PART # DESCRIPTION REFERENCE DESIGNATION
5 REF SCREW M) 4X30 BLK T/H @ CAB BACK
1 0072797000 SPEAKER 10" 8 OHM G-DEC 30
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
- 0053997000 **CORD PWR W/IEC CONN 100V JPN 100V JPN ONLY
1 0072802000 *BADGE G-DEC 30
2 REF SCREW T) 2.1X10 NIP R/H @ BADGE
1 0029906000 *NAMEPLATE FENDER GENERIC
2 REF SCREW T) 2.8X12 BLK O/H @ NAMEPLATE
1 REF MANUAL OWNERS G-DEC 30
4 REF SCREW NO. 8 U32X30 BLK O/H @ CHASSIS
3 REF SCREW M) 3.5X10 BLK T/H @ CHASSIS REAR
4 REF WASHER BLK FINISHING TYPE @ CHASSIS
*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.