This service manual is intended to assist trained and qualified technical personnel in verifying the
performance of, adjusting, and repairing the ADCOM GFP-710 preamplifier. The procedures described
here are not intended for persons unfamiliar with the appropriate safety and test procedures.
WARNING
THERE ARE POTENTIALLY LETHAL VOLTAGES WITHIN THE GFP-710 PREAMPLIFIER WHICH
WILL BE ACCESSIBLE ONCE ITS TOP COVER IS REMOVED. DO NOT ATTEMPT
FAMILIARIZATION, INSPECTION, OR ANY PROCEDURE WHATSOEVER UNLESS YOU HAVE
DISCONNECTED THE GFP-710 FROM THE WALL AC OUTLET OR OTHER SOURCE OF AC
POWER AND THE POWER-SUPPLY CAPACITORS ARE COMPLETELY DISCHARGED. THESEINSTRUCTIONS ARE PROVIDED FOR USE ONLY BY COMPETENT TECHNICAL PERSONNEL. DO
NOT UNDERTAKE ANY SERVICE PROCEDURES IN THE GFP-710 UNLESS YOU ARE
TECHNICALLY QUALIFIED TO DO SO.
25001060 AC Inlet 25001010 AC Outlet 15001120 AC POWER CORD 13001050 Bottom Plate 11001180 Button w/ hole 11001130 Button w/o hole 13001020 Foot 12000712 Front Chassis 13000710 Front Panel 19000100 FUSE 1A 250V
20003200 Fuse Holder 23001070 Volume Knob 23001000 Bass/Treble/Bal knob 11001155 Power Button 24000710 Power Transformer 13000711 Printed Rear Chassis 13000713 Side Chassis 13003032 Side Chassis (R) 11001170 Tact Button Connector
27002360 Resistor Roed 562
5
11001160 Tact Button Connector 13001040 Top Cover
6
a
GFP-710 VOLTAGE CONVERSION
115V TO 230V
1. The multivoltage GFP-710 units have a detachable power cord and no rear panel AC outlets.
2. Unplug the unit and remove the top cover.
3. On the AC primary board mounted at the far left of the unit, unsolder the jumper at the 115V
position and move it to the 230V position. Also, check the MOV position and type. Figure 1.
4. Change the rear panel fuse from 1A/250V to 500mA/250V. Also, remove the 1A/250V sticker
above the fuse holder so the 500mA/250V panel writing is visible.
5. Remove the 120V sticker at the far left of the rear panel so the 220-240V writing is visible.
6. Replace top cover and test unit.
Move jumper here
240V MOV should be here.
AC5
AC4
Type 12G431K.
Adcom part #:12001615.
230V
115V
AC3
Figure 1: 220V Jumper position
AC2
AC1
230V TO 115V
1. The multivoltage GFP-710 units have a detachable power cord and no rear panel AC outlets.
2. Unplug the unit and remove the top cover.
3. On the AC primary board, mounted at the far left of the unit, unsolder the jumper at the 230V
position and move it to the 115V position. Also, check the MOV position and type. Figure 2.
4. Change the rear panel fuse from 500mA/250V to 1A/250V. Also, place a 1A/250V sticker above
the fuse holder to cover the 500mA 250V writing.
5. Place a 120V sticker at the far left of the rear panel to cover the 220-240V writing.
6. Replace top cover and test unit.
Move jumper here
Main outputs............................................................................................................................................................... 100 ohms
Main Outputs....................................................................................................................................................................... 2.0V
Main Outputs.................................................................................................................................................................. ≥ 10.0V
Frequency Response (+0.5 db)
High Level............................................................................................................................................................. 5Hz – 50KHz
High Level...................................................................................................................................................................... 0.005%
High Level...................................................................................................................................................................... 0.005%
High Level.....................................................................................................................................................................≥ 100 db
Phono...............................................................................................................................................................................≥95 db
Input Impedence
High Level...................................................................................................................................................................25K ohms
High Level...................................................................................................................................................................... 205 mV
Bass (20Hz).............................................................................................................................................................. +/- 11.5 db
Phono (20KHz)........................................................................................................................................................... +/- 8.5 db
Power Consumption...................................................................................................................................................... 10 watts max
Power (Available in 230VAC on special order).................................................................................................... 115VAC - 50/60Hz
Chassis Dimensions................................................................................................ 3” (76mm) x 17” (432mm) x 11 3/8” (289mm)
Maximum Dimensions.................................................................................... 3 1/4” (83mm) x 17” (432mm) x 12 8/16” (319mm)
Weight.............................................................................................................................................................................. 12 lb. (5.5 kg)
Weight, Packed............................................................................................................................................................... 15 lb. (6.8 kg)
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