Adcom GFA 4402 Service Manual

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SERVICE MANUAL

ADCOM®

details you can hear

CAR AUDIO
POWER AMPLIFIER

GFA-4402

TABLE OF CONTENTS
Introduction ....................................... 2
Specifications and Features ............. 3
Wiring Configurations ....................... 4
Parts Lists ......................................... 5
Notes ................................................. 8
Schematics ........................................ 9

DCOM'

TECHNICAL SERVICE DEPARTMENT
11 ELKINS ROAD
EAST BRUNSWICK, NJ 08816
PHONE: (900) 390-1130
FAX: (908) 390-9152

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Welcome To ADCOM Car Audio

The ADCOM GPA-4000 series car amplifiers offer the consumer a new level of sound quality in the mobile
environment. Audiophile sound quality is now unleashed to the streets in what ADCOM calls The
Ultimate Power Trip".

in servicing the GFA-4ODO series amplifiers you will see the straight forward, bare bones, high quality
construction, and attention to detail that has been engineered into this line of power amplifiers. You will
see that most repairs are very straight fonNard, and easily located.

Attention to the hook-up of these amplifiers is essential, as the amplifier will not perform optimally if not
configured properly. The biggest difference you will find in hook-up of these amplifiers is the input
configuration. The GPA-4000 series uses a Balanced Input configuration. As you know this reduces
noise induced into the amplifier at the input. For more information on the hook-up, and on the theory
behind the Balanced Input configuration, please refer to the Technical Details Manual.

The GPA-4402 amplifier produces 40 watts HMS into a 49 load. The amplifier can be configured to run in
a bridged mode, and is stable into a 1 0 load. The input to the amplifier consists of four (4) RCA
connectors, in a Balanced Configuration. There are 2 RCA connectors per channel, one for the positive
input and one for the negative (out of phase) input. The other balanced mode which is called Passively
Terminated Balanced Configuration, has the signal applied to the positive input. and the "signal" ground
(chassis) of the head unit applied to the negative input. The amplifier can also be used in the bridged
mode or the MoEitm (Mono + Stereo) configuration. Basic diagrams are displayed on page 4. For more
detailed configurations. refer to the Owners Manual or the Technical Details Manual.

The GFA-4402 provides level controls for the positive input, these should be set at full during testing.
When bridging the amplifier, the input is applied to the positive input of one channel (i.e. - Ch A), and the
negative channel of the other channel (i.e. - Ch B). The Speaker (or load) is then connected as so; A+ is
the positive load, and "8+" is the negative lead. RCA shorting plugs must be inserted into all unused input
jacks for proper operation.

Service Notes: .

0 The enclosed schematics are version 1.4, and include all current updates to the original design. if you
encounter changes in the circuit on a unit you are servicing. please call ADCOM Service, at (908)390-
1130, to find out if the changes are factory authorized, if the unit was modified by a third party, or if the
unit is from a production run prior to the implementation of the printed updates. Also see page 8 for
most common differences.

0 When replacing parts in the GFA-4000 series amplifiers, always use the same type, and rating.

0 When replacing the MOSFET devices, use only the same type of devices removed. The MOSFET
devices also must be matched in the output stages and front end circuits. Use care as these are
static sensitive devices, and require all special handling precautions associated with static sensitive
devices.

Remember that ADCOM Service is available from 9:00 AM to 5:00 PM EST for inquires, or you can fax
us at (908)390-9152.

This service literature may chance at anv time without notice,

K.Karagan 6/1/95

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GFFl-4402 PARTS LIST

DIODES
D1 ________________________ 16.999251 ,,,,,, 14515.4 50 volt 6 amp high surge
'0101 116001610 16CPF10 dual common cathode
D102 16001611 16JPF10 dual common anode
D103,104, 105,106 16004735 1N4735 6.2 volt 1 watt Zener
D 4.05.- 503 595W ..
402, 303, 304 16004936 _____ 1N4935 1 amp 1as1 recovery 2.. __
D305 ______»_, "16004744 M1N4744 15 volt 1 watt Zener
0401 402,404,406 16004738 1N4738 8. 2 volt1 watt Zener
D501, 502, 503, 504
D407, 507 16004148 1N4148 100 mA signal diode
CHASSIS PARTS
TOP 13004021 Black 4402 Top Cover
13994023 White 4402 Top Cover
BOTTOM 13004022 Black 4402 Bottom Chassis
1 130040247 __________ White 4402 Bgfiom Chassis
ENDCAP: 2 Channel 13000001 Black 2- Ch Connector-End Endcap
13000004 White 2- Ch. Connector-End Endcap
ENDCAP: Vented 13000003 Black Vented-End Endcap
13000006 White Vented-End Endcap
FAN COVER 13004026 Black 4402 ADCOM Fan Cover
117117117771113004027 White 4402 ADCOM Fan Cover
PERF SLEEVE 13004025 Black 4402 Perforated Vent Sleevemm
HEAT SINK 13000011 4402 Tunnel Heat Sink
INS. SHEET 13000017 4402 Chassis Insulator Sheet
VJLARQE STICKER LABEL34 figggflgular "bal inputs Sticker w
LONG 4402 STICKER LABEL32 Long model GFA-4402 Sticker
MISCELLANEOUS
J101 124001110 4 Pin RCA Jack Board
FAN1 . 13001000 100mm DC Cooling Fan
TEFlM1, 2 30001100 Large (7/16) Gold Power Terminal
TERMS, 4, 5, 6, 7 30001200 Small (5/16) Gold Speaker Terminal _
LG SET SCREW 30001101 7/ 16 Hex Set Screw 1or Large Terminals
SM SET SCREW 30001201 51/16" Hex Set Screw for Small Terminals
SP1, 2 22001000 RCA Snorting Plug .,-__
FH-ATC 20002050 ATC Fyge Harness Loop
FUSE 19003000 _ 30 Ampere ATC Fuse
PCB-TO 36001250 Tum-On PC Board

' schematic on page 8