Yamaha a 720

Page 1

YAMA-00132

STEREO INTEGRATED AMPLIFIER

A-720

SERVICE MANUAL

I FRONT PANEL

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I CONTENTS

TOSERVICEPERSONNEL.................

SPECIFICATIONS
REAR PANELS . ..
BLOCK DIAGRAM
INTERNAL VIEW .

IMPORTANT NOTICE

This manual has heen provided for rho use or authorized Yamaha Renllers and [hclr service persrnnei.
II has been assumed that bash. serwcc procedures inhcrani to the industry, and more speciricaily Varnaha
Products, ale already known and undersrood by the users, and have therefore not been resiared,

WARNING: Failure to Iollow appropriate seryicc and safely procedures when servicing this product
may result in personal intury. destrucnon oI expensive componems and failure 0f rhe
product to perform as specified. For these reasons, we advise all Yamaha productoiyncrs
that all sema- rcquered should be perlormcd by an authorized Yamaha Retailer AI' the
appoinlcd 5min: representative,

IMPORTANT: The presentation or sale of this manual to any indivrdual or firm does not constitute
authorization, certification, recognition of any applicable technical capzbilitits. or
establish a principle agent relationship of any form.

The data prawded ls believed to be accurate and apuIiLable to the unit]; indicated on the cover The
research, engineering, and service departments of Vamaha are continually strivmg to improve Yamaha
products. Modifications are, thercicre, inevitable and changes in specificamn are subject to change wilhout
nolioe or obligation to retrofit, Should any discrepancy appear to exist, please Contact me distribators
Service Division.

WARNING: Static discharges can destroy expensive components. Discharge any static electncityyour
body may have accumulated by grounding yourself Io the ground buss in the uni! (Aeavy
gauge black wires connect to this buss).

IMPDRTANT: Turn the unit OFF during disassembly and parts replacement. Recheck all work bzfore
you apply power to the unit.

ADJUSTMENTS . . . . . . . . ..
PRINTED CIRCUIT BOARD ..
SCHEMATIC DIAGRAM I .. ..

WIRING .. ...... ..

DISASSEMBLY PROCEDURES 21.2,...

PARTSLIST...........I

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a YAMAHA

NIPPON GAKKI 60., LTD. HAMAMATSU , JAPAN
2.5mm. n®

Page 2

A-720

ITO SERVICE PERSONNEL

1. Critical Components information.
Components having special characteristics are marked
! and must be replaced with parts having specifica-
tions equal to those originally installed.

2. Leakage Current Measurement (For 120 V Model
Only).
When service has been completed, it is imperative that
you verify that all exposed conductive surfaces are
properly insulated from supply circuits.

0 Meter impedance should be equivalent to 1500 ohm
shunted by 0.15uF.

O Leakage current must not exceed 0.5mA.

0 Be sure to test for leakage with the AC plug in both
polarities.

I SPECIFICATIONS

EQUIPMENT Ac LEAKAGE TESTER
UNDER TEST on EQUIVALENT
® 0- «-
WALL t: -[_
OUTLET INSULATING TABLE "

Continuous Power Per Channel

ZOHZ ~ 20kHz (0.005% THD. 3n) 105W
(0.007% THU, 63!) 125W
1kHz, [EC Rated Power
(001% THD. 3.0.) 117W (R)(U)(C)
110W (A)(E)
(0.01%THD.60.) 143W(H)(U)(C)
144W (AHE)
DIN Standard Output Power Per Channel
1kHz(1%THD.4Q) 150W(A)(E)
Dynamic Headroom
357. 1.4dB
60. 1.58dE
Dynamic Power Per Channel (IHF)
80 145W
6n 180W
4&1 240W

Power Band Width
003% THD. 52.5w an

Dimping Factor

10Hz ~50kHz

1kHZ, 8n (SPEAKER A) 45
Input Sensitivity/Impedance
Phone MC ISOILV/ZZOQ
MM 2.5mV/47kn
CD/AUX/TAPE/TUNER I50mV/47kfl
Input Sensitivity [New IHF)
Phono MC 16MV
MM 0.25mV
CD/AUX/TAPE/TUNER 15mV

Maximum Input Signal

1kHz,0.01%THD, Phono MC 10mV
MM 165mV
Output Level/Impedance
Rec Out 150mV/470S2
Headphone Jack Rated Output/Impedance
0.005% THD 0.83V/8fl
Frequency Response +0
20H: ~20i (TONE EVPASS ON) '
HlAA Equalization Deviation
20H: ~ ZOkHz, Phono MC $0.3dE
MM £0.2dB
Total Harmonic Distortion
Phono MC to Rec Out 3V 0.006%
MM to Rec Out 3V 0.003%
CD/AUX/TAPE/TUNER to SP Out 0.005%
(52.5W/8f2)
lnterrnodulation Distortion
CD/AUX/TAPE/TUNER Rated Output/857. 0.002%
lW/8SI 0.003%

Signal to Noise Ratio (lHF-A-Network)

Phono MC (BOOHV Input Shorted) 76dB
MM (SmV lnput Shorted) ' 92dB
CD/AUX/TAPE/TUNER
(Input Shorted, TONE BYPASS 0N) 106dB
Signal to Noise Ratio (New IHF)
Phono MC 74.5dB
MM 78dB
CD/AUX/TAPE/TUNEFI 85dB
Input Equivalent Noise
Phone MC -142dBV (AHE)
MM -l38dBV (ANE)
Residual Noise [IHF-A-Network)
TONE BYPASS ON 133MV

Channel Separation
Phono MM (1 kHz, Input shorted, Vol -30dB) 70118
CD/AUX/TAPE/TUNER (1kHz, 5.1kfl, Vol -30dB) 85dB

Tone Control Characteristics

BASS boost/cut #10dB (20Hz)
turnover irequencv 350Hz
TREBLE boost/cut ilOdB (20kHz)
turnover frequency 3.5kHz

Filter Characteristics
Low (Subsonic) 15Hz, ~12dB/oct

Continuous Loudness Control (Level-related equalization)

Attenuation --40dB (1 kHz)
Audio Muting -20dB
Gain Tracking Error (0 to -60dB) 2dB
Power Supply

U.S.A. & Canadian models 120V AC, 60H:
General model 110V/120V/220V/240V AC, 50/60Hz
European model 220V AC, 50H:
Australlan model 220V/240V AC, 50H2
Power Consumption 360W, 450VA (U)(C)
240w (Fl)

360W (A)

470W (E)

AC Outlet (U)(CI(R)
Switched x 2 200W max total (R)
100W max total (U)(C)
200W max

435 x147 x 399 mm
(17-1/8" x 5-3/4" x15-3/4")

10.2 kg (22 lbs 7 oz)

Unswitched x 1
Dimensions (W x H x D)

Weight

Specifications are subject to change without notice.

(U) U.S.A. model
(C). Canadian model
(A) . Australian model
(E) . European model

(R) . General model