Yamaha A-760II User manual

sE EO I
L I F I E fi3 ~
TE q~h TE DAM
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SE
VICE MAN
. FRONT PANEL
1
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:~-: ; ~ :: ; ~ ~' ; •
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.-
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.
,T
.~
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· (\ . " 1'1" "
·
· .. . -.
. ' 1" , : I
Power Switch
Treble Control
f) Listening Level Monitor
.. High Filter
Main Direct Switch
Loudness Control
Disc Switch Balance
Control
Muting
Switch
a. Mode Control
(1) Volume Control Phono Select or
Speaker Switch Rec
Out Sele ctor
o Phones Jack
f) Input Selector
Bass Control
. CONTENTS
Rear panel. . . . • . . . . . . . . . . . . . . . . . . . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . . • . . . . . . . . . . . . . 1
Names of
the Parts 2
Disassembly
Instructions . . . . . . . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . . . . . . . . . . . . . . . .. 3
Specifications . . . . . . . . . .. . . . . . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . • • . . • . . . . . . . • . . . . . . . . 5
Adjustm ents . . .. .. . . . . . . . . .. . . . . . . . . . . . . . . ... . . . .. . . . . . • . . • . . . . . . . . . . . . . • . . . . . . . 6
Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . . . . • . 7
Printed Circuit Layout. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . . . . • . . . . 7
Printed Circuit Board/Wiring _ . . . . . • . . . . . . . . . . .. 9
Complete Circuit Diagram 10
3 ~
SINCE 1887 • YA MAH
I004458 I " NIPPON GAKKI CO.. LTO. HAMAMATSU, JAPAN
. 82 . 3.2 .65K f { ~ Pnnted rn Japan,

• ••
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A-760 n
.REA R PANEL
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----'@
U.S.A and Canadian Models
Gnd
ter minal o Tape 1 ,2 record /playback [acks
Phono input jacks Speaker A. B ter minals
Tuner input jacks o AC
outlets
o Aux input jacks o Power
cord
r ] <..sz "" ~I
OYAMA HJI ~ ~
~~ ~ eaowerrs @]
---
IItPPOllaW CQ.UD.
Austr alian and British Models
... ....
O Y AM A HA ~ ~
~ ~ s ~ :.oo Wll. ns lQl
NIPPONGAUl ce, lT'D.
European Model
OYA M A HA ~ ~
HO 12'0 2::.>0»4 0 1IQ.1'S
3:C""",rrs :.a /OO Hl -c,
ro Jt GUJtI C D..UD.
•••
• ••
General Model
1------------------- -------------- --

A-760 1I
• NAME OF THE PA TS
Internal Top View
U.S.A and Canadian Model
AC
outlet
Muting switch
Power cord Disk switch
Power transformer
il Main Direct switch
Main board 2 (
NA07 861·2) Tone
control board 1 (NA07859-1)
Heat sink Main board 4 (NA07861-4)
Power transistor Main board 5 (NA07861-5)
Main board 1
(NA07 86 1·1l
Power switch
Function board
(NA07857)
Primary board 1
Tone control board 3
(NA07859-3l
Primary board 2
Tone
control board 2 (NA07859 -2)
--------- -------------------------2

DISAS SEMBLY INSTRUCTIONS
1. Remo ving the top cover
Remove screws
CD and 0 on each side, per photo
1 and remove the top cover by pulling back and
lifting up,
4. Removing
the rear panel
a) Remove
the top cover (step 1).
b) Remove
the bottom cover (step 2).
c) Remove screws
CD ~ @ . The
be taken off. cover can then
2. Removing
the bo tt om cover
Flip
the A-760II over and remove screws CI) ~ ®
in phot o 2; then remove the bottom cover.
Photo 2
3. Removing th e fron t panel
a) Remove
the top cover (step 1).
b) Remove
the bottom cover (step 2).
c) Loosen
the Speaker, Rec Out and Input knobs with
a 1.5 mm allen
wrench. PuHeach knob off its shaft.
d) Disconnect
the wires from the Power, Main Direct,
Disc and Muting switches being carefule
not to
brake
them.
e) Remove screws CD and 0 in photo 3 and remove
the front panel by pulling forward.
Photo 4
5. Removing the function board
a) Remove the top cover (step 1).
b) Detach
the various cords and connec to rs; then
detach the flexible wire fro m each switch with a
screwdriver. (Fig. 1)
c) Take out screws @ ~ @ photo 4 to remov e the
function board.
Fig.l
6. Removing tone control boards 1, 2, and 3, main
boards 4 and 5 and the power switch
a) Remove
the top cover, bottorn cover, and front
panel (steps 1,2,3).
b) Pull off the Bass, Treb le, Loudness, Balance and
Volurne
controls.
c) Tone control boards 2 and 3 can be removed by
taking
out nut ® and screws G) ~ ® in p hoto
5,
d) Tone control board 1 can be rernoved by taking out
screws (j) and ® and nuts ® ~ ® in ph oto 5.
e) Main board 4 is rem oved by ta king
out screws
®and @ and pulling off the Lis tening Level
Monitor
knob in pho to 5.
f) The power switch can be removed by removing
screws @
and @ in phot o 5.
g) Main board 5 can be rernoved by pu lling out the
phone iack fastener ® in ph oto 5 in th e direction
of
the arrow.
3---------- ---------- ---------------

7. Rem oving main board 1 and the heat sink
a) Remove the top and bottom covers,
b)
Remov e the function board (step 5).
c) Desolder
power transistors TR335 - TR338.
d) Take out main board 1 by removing screws CD -
®in photo 6.
e)
Detach connectors ® - @ in photo 6.
f) Remove the heat sink by taking out screws ®-
® in photo 6.
*Make sure that transistors TR321 and TR322 are
correctly
connected to the heat sink for proper heat
dissipation,
Photo 6
A-760 II
8. Removing the power tran sform er and pr imary
boards 1 and 2
a) Remove
the top cover (step 1).
b) Remove
the primary board wiring.
c)
Take out screw CD in photo 7 and release pr ima ry
boards 1
and 2 from board fasteners ® and ® .
d) Remove the power transformer cover by taking out
screws ®- ®in photo 7.
e)
Take out screws CD - 8) in photo 8 to remove
the power transformer .
Photo 8
------- -------------------------- --4

.SPECIFICAT IONS
Minimum RMS Output Power Signal-to-NoiseRatio (NEW IHF)
8 ohms, 20 to 20, OOOHz (Main Direet ON) Phono MM _ _. _ 74.5 dB
0.005% THD 80 W + 80 W Phono MC .
__ 78 dB
8 ohins, 1 kHz 0.002% Aux/Tape/Tuner 85 dB (Main Direct
THD . 80 W + 80W
ON)
4 ohms elipping power Residual Noise
. 1 k H ~ 0.5% THD 150 W + 150 W (lHF A Network) .
__ . . . . 65 p.V
Total Harmonie Distortion
Input Equivalent Noise
(20 Hz to 20 kHz) Phono MM - 138 dBV
Phono
MM ·to Ree Out Phono MC _ - 142 dBV
(5 Vou tput! 0.003% Filter Charaeteristics
Phono MC to Ree Out High 10 kHz, 12
dB/o ct.
(5 V output] 0.006% Channel Separation
Aux/T ape /Tu ner to Sp (1 kHz, vol.
-30 dB, Shorted)
Out
(40 W, Main Direet Aux, Tuner to Sp Out 70 dB
ON) . : ' 0.005% Phono MM to Sp Out
.. . . 70 dB
IM Distortion Ratio (60 Hz : 7 kHz =4 : 1) Phono MC to Sp
Out. . . . . 70 dB
Aux/Tape/Tuner to Sp Out Continuous LoudnessContral
8 ohms, 80W . . . . . . . . . 0.002% (Level-Related Equalization)
8 ohrns, 1 W 0.01% Max. Attenuation 20 dB at 1 kHz
Power Bandwidth (Main Direet
ON)
Audio Muting _ . .
-20 dB
(8 ohms, 40 W, 0.02% Gain Traeking Error
THD) . . : , 10 Hz to 100 kHz (0 to
-60 dB) _. . 2 dB
Damping Faetor Headphone Output/lmpedance
(8 ohrns, 1 kHz) . Better than 65 (0.01%
THD) 0.72 V/8 ohms
Frequency
Response
6.8 V/ 100
ohm s
( Au x t ~a p e / T u n e r to Sp Power Supplies. . . . . . . . . . . 120 V. 60 Hz (U,C)
Out, 8 ohms) .
.. . . 1 Hz to 100 kHz 220 V. 50 Hz (G,W)
," (+0,
-2 dB)
240 V, 50 Hz (A, B)
RIAA Deviation 110/1 2
0/ 22 0/ 240 V,
Phono
MM . ± 0.2 dB 50/60 Hz (R )
Phono MC . ±
0.3 dB Power Consumption . , . . . . . 350 W/
850 VA (Cl
Input Sensitivity/lmpedance 350 W (U, R)
Phono MM . 2.5
mV /47 k ahms 520 IN (A, G, B, W)
Phono'MC . 160 JJV/ 100 ohms AC Outlets
Aux/Tape/Tuner . 150
mV /47 kohrns Switehed x 2 . 100 W max total
Maximum Input Level (1 kHz) Unswitched
xl . . . . . . . .
200 W max
Phono MM . 180 mV RMS Dimensions (W x H x D)
... . 435 x 112 x 365 mm
Phono MC . 10 mV RMS (17-1/8" x 4-7/1 6" x
Tone Control Charaeteristies 14
-3/ 8" )
Ba
ss . ± 10 dB at 20 Hz Weight . . 9.1 kg (20 lbs., 7 oz.)
Tr eble . ±lOdBat20kHz
Turnover Frequeneies Specifieations subjeet to change without notiee.
Bass . 500 Hz
Treble . 3.5 kHz U :
USA. Model
Output Level/lmpedance C : Canadian Model
Ree Out . 150
mV /270 ohms R : General Model
Signal-to-Noise Ratio A : Au stralian Mod el
(I HF A Network, Input B : British Model
Shorted) G : European
Mod el
Phono M
(5 mV) .... . 92 dB W : West Ger
many Model
Phono MC (500 JN)
..
76 dB
Aux/Tape/T uner 106 dB (Main Direct
ON)
5--------------------------------

A-760 II
GENERAL A JUSTMENTS
Before adjustment
• Make sure that t he AC line is ± 10%
• Wait 5 minutes aft er power-on
to stabilize amplifier operation
Test
Step Adjustment
Conditions Loeation Test Point Value
Equipment
:
Main B +"B-
Between chassis ground Digital
Main board 1
voltage ad- No load and P1 terminal of pri- 47.5±O.3V
voltmeter
1
VR303
justment mary board
(test er)
Between P1 and
TP3 of the primary board 1.2V±O.1V
Photo coup -Minimum volume, (if
out of ranqe, turn to VR501 and VR303
(2 .0V±0 .1V
same as
2 ler
cur r ent
no load and
adjust B+, B- and P1 - TP3 =FEMKO, above
che ck* for
rated voltages) DEMKO)
Main
board 1.
Idling
TP3 - TP4 (L), same as
3 Minimum volume VR301 (L ch) ,
6.6 :g mV
adjustment
TP1 - TP2 (R) abo ve
VR302 (R ch)
Output off - L. R within
same as
4 Minimum volume Speaker
terminals
set check o± 30 mV above
* It is
not necessary to check the photo -coupler current of step 2 except when replacing the photo -coupler,
Also, perform steps 1 and 2
simultaneously (with two digital voltmeters).
ADJUSTMENT LOCATION DIAGRAM Main c.
board 1
D
VR301 (L ) VR30
2lRl
TP3 @ @
Primary c. board 1 c
00
TPI
TP4 c
c TP2
c
VR501 o0
0501 0
10
TR501 TP5
o
D o
• TP7
rp6
c
o
Pl mTP3
FRONT
Primary c. board 2
------- -------- --------- ----------- - - -6

A-7601I
- J
BL CK DIAGR AM
/.-
ZDR
oe SER....O
TONE AMP HIGH POWER ..tMP
REC INPUT DISC MODE FILTER LOUDNESS
PHONO MUTING 1\ \
BALAN CE \\
\ } {\
' , BASS TREBLE \
~ - - --- - - ---- - - - --- ---- ------ - -~
VOLUME
AUX
TUNER @-----~--- t___1
~H EA DP HO N E
PB '
TAPE PB 2
TAPE
t- - - --< 7"'i : ~ SPEAKER
REC 1 "'ROf
fer tON ; ~ ~ ~ ~ ~ R
REC 2
~ ---- .- -- -'
,
POWER SWITCH
-0 ':-0-
+47.5 V constant
A CI N
--47.5 V constan t
. PRIN lE D CIRCUIT BOARD PAnERN-SIDE COMPONENTS LAYOUT
Primary c. board (Australian, British and European Models)
~
' ,
~U
TR ~ O I
..
n J J ~
,....---------,~I===I= I= I==
7----------------------------------

8----- --------------- ---------- ---------
Lpaeoq ":l I O J ~ U O:l auoj,
e ...

PRINTED CIRCUIT BOARD PATTERN-SIDE COMPONENTS LAY OUT
Primary c. board (U. S. A and Canadian Models) Primary c. board (General M
odell
Function circuit board Main e, board 5
Tone control c. board 3 Tone control c. board 2