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STEREO RECEIVER
RX-777 SERVICE MANUAL
IMPORTANT NOTICE
This manual has been provided for the use of authorized YAMAHA Retailers and their service personnel.
It has been assumed that basic service procedures inherent to the industry, and more specifically YAMAHA Products, are already
known and understood by the users, and have therefore not been restated.
WARNING: Failure to follow appropriate service and safety procedures when servicing this product may result in personal
injury, destruction of expensive components, and failure of the product to perform as specified. For these reasons,
we advise all YAMAHA product owners that any service required should be performed by an authorized
YAMAHA Retailer or the appointed service representative.
IMPORTANT: The presentation or sale of this manual to any individual or firm does not constitute authorization, certification or
recognition of any applicable technical capabilities, or establish a principle-agent relationship of any form.
The data provided is believed to be accurate and applicable to the unit(s) indicated on the cover. The research, engineering, and
service departments of YAMAHA are continually striving to improve YAMAHA products. Modifications are, therefore, inevitable
and specifications are subject to change without notice or obligation to retrofit. Should any discrepancy appear to exist, please
contact the distributor's Service Division.
WARNING: Static discharges can destroy expensive components. Discharge any static electricity your body may have
accumulated by grounding yourself to the ground buss in the unit (heavy gauge black wires connect to this buss).
IMPORTANT: Turn the unit OFF during disassembly and part replacement. Recheck all work before you apply power to the unit.
s CONTENTS
TO SERVICE PERSONNEL .......................................... 1 TEST MODE ................................................................... 6
IMPEDANCE SELECTOR ............................................. 1 DISPLAY DATA ............................................................. 8
REAR PANELS .............................................................. 2 IC DATA ................................................................... 9~10
SPECIFICATIONS .......................................................... 3 PRINTED CIRCUIT BOARD .................................. 11~22
INTERNAL VIEW ........................................................... 4 BLOCK DIAGRAM ................................................. 23~24
DISASSEMBLY PROCEDURES ................................... 5 SCHEMATIC DIAGRAM ........................................ 25~28
RX-777
OPERATION P.C.B. CHECK ......................................... 5 PARTS LIST ........................................................... 29~38
AMP ADJUSTMENTS .................................................... 6 REMOTE CONTROL TRANSMITTER ........................ 39
100749
P.O.Box 1, Hamamatsu, Japan
RX-777
s TO SERVICE PERSONNEL
1. Critical Components Information AC LEAKAGE
Components having special characteristics are marked Z WALL EQUIPMENT TESTER OR
and must be replaced with parts having specifications equal OUTLET UNDER TEST EQUIVALENT
to those originally installed.
2. Leakage Current Measurement (For 120V Models Only)
When service has been completed, it is imperative to verify
that all exposed conductive surfaces are properly insulated
from supply circuits.
INSULATING
q Meter impedance should be equivalent to 1500 ohm shunted TABLE
by 0.15µF.
q Leakage current must not exceed 0.5mA.
q Be sure to test for leakage with the AC plug in both polarities.
WARNING: CHEMICAL CONTENT NOTICE!
The solder used in the production of this product contains LEAD. In addition, other electrical/electronic and /or plastic
(where applicable) components may also contain traces of chemicals found by the California Health and Welfare Agency
(and possibly other entities) to cause cancer and/or birth defects or other reproductive harm.
DO NOT PLACE SOLDER, ELECTRICAL/ELECTRONIC OR PLASTIC COMPONENTS IN YOUR MOUTH FOR ANY REA-
SON WHATSOEVER!
Avoid prolonged, unprotected contact between solder and your skin! When soldering, do not inhale solder fumes or expose
eyes to solder/flux vapor!
If you come in contact with solder or components located inside the enclosure of this product, wash your hands before
handling food.
s IMPEDANCE SELECTOR
IMPEDANCE SELECTOR
RX-777
WARNING:
Do not change the IMPEDANCE SELECTOR
switch setting while the power to this unit is
on, otherwise this unit may be damaged.
1
RX-777
s REAR PANELS
U model
C model
A model
RX-777
2
RX-777
s SPECIFICATIONS
s AUDIO SECTION s AM Section
Minimum RMS Output Power (Power Amp. Section) Tuning Range
8 ohms, 20 Hz to 20 kHz, 0.019% THD ................. 100W + 100W [U, C models] ..................................................... 530 to 1,710 kHz
6 ohms, 20 Hz to 20 kHz, 0.03% THD ................... 120W + 120W [A model] ............................................................ 531 to 1,611 kHz
Dynamic Power Per Channel (IHF) Usable Sensitivity
8/6/4/2 ohms .................................................. 140/170/220/290 W ........................................................................................ 300 µV/m
Power Band Width Antenna
8 ohms, 50W, 0.03% THD ................................... 10 Hz to 50 kHz ................................................................................. Loop Antenna
Damping Factor
8 ohms, 20 Hz to 20 kHz, SPEAKER-A .................... 240 or more
Input Sensitivity / Input Impedance s Video Section
PHONO MM ................................................... 2.5 mV / 47 k-ohms Video Signal Type
CD, etc. ......................................................... 150 mV / 47 k-ohms [U, C models] ....................................................................... NTSC
MAIN IN ................................................................ 1 V / 30 k-ohms [A model] ................................................................................. PAL
Maximum Input Signal Level Video Signal Level
PHONO MM (1 kHz, 0.015% THD) .................................. 115 mV ............................................................................ 1 Vp-p / 75 ohms
CD, etc. (1 kHz, 0.015% THD) ............................................. 2.2 V
Maximum Input Level
Output Level / Output Impedance .......................................................................................... 1.5 Vp-p
PRE OUT ............................................................ 1 V / 1.2 k-ohms
REC OUT (PHONO) .................................... 150 mV / 1.7 k-ohms Signal to Noise Ratio
................................................................................. 50 dB or more
Headphone Jack Rated Output / Impedance
0.015% THD, 8 ohms, 1 kHz, 150 mV ............ 0.47 V / 470 ohms Monitor Out Frequency Response
.................................................................... 5 Hz to 10 MHz, -3 dB
Frequency Response
CD, etc. (20 Hz to 20 kHz) .............................................. 0±0.5 dB
MAIN IN (20 Hz to 20 kHz) ............................................. 0±0.5 dB
CD (CD DIRECT AMP ON, 20 Hz to 100 kHz) .............. 0±1.0 dB s General
RIAA Equalization Deviation Power Supply
PHONO MM (20 Hz to 20 kHz) .................................... 0 ± 0.5 dB [U, C models] ...................................................... AC 120 V, 60 Hz
Total Harmonic Distortion [A model ] ............................................................ AC 240 V, 50 Hz
(20 Hz to 20 kHz) Power Consumption
PHONO MM, to REC OUT (3 V) ........................... 0.008% or less [U model] ............................................................................. 260 W
CD, etc. to PRE OUT (1 V) .................................... 0.007% or less [C model] ............................................................................. 210 W
CD, etc. to SP OUT (50 W / 8 ohms) .................... 0.012% or less [A model] ............................................................................. 200 W
Signal to Noise Ratio (IHF-A network) Standby Power Consumption
PHONO MM (5 mV Input shorted) ......................... 87 dB or more [U, C models] ....................................................................... 0.9 W
CD (CD DIRECT AMP ON, 150 mV Input shorted) .... 110 dB or more [A model] .............................................................................. 1.0 W
Residual Noise (IHF-A network) AC Outlets
CD DIRECT AMP ON .......................................................... 30 µV [U, C models]
PURE DIRECT ON ............................................................ 110 µV 2 switched outlets ............................................... 100W max. total
Channel Separation [A model]
CD, etc. (Input 5.1 k-ohms shorted, 1 kHz) ............ 65 dB or more 1 switched outlet ......................................................... 100W max.
CD, etc. (Input 5.1 k-ohms shorted, 10 kHz) .......... 50 dB or more Dimensions (W x H x D)
Tone Control Characteristics ................. 435 x 151 x 390.3 mm (17-1/8" x 5-15/16" x 15-5/16")
Bass: Boost/Cut ................................................ ±10 dB (20 Hz) Weight
Turnover Frequency ............................................ 350 Hz .................................................................... 9.8 kg (21 lbs. 10 oz.)
Treble: Boost/Cut .............................................. ±10 dB (20 kHz)
Turnover Frequency ........................................... 3.5 kHz Finish
...................................................................................... Black color
Continuous Loudness Control
Attenuation, 1 kHz ............................................................... -30 dB Accessories
..................................................... Remote control transmitter x 1,
Gain Tracking Error Manganese batteries (size "AA", "R06") x 2,
0 to -60 dB .................................................................. 2 dB or less Indoor FM antenna x 1,
AM loop antenna x 1
* Specifications are subject to change without notice.
s FM Section
Tuning Range U .......... U.S.A. model C ...... Canadian model
[U, C models] ................................................... 87.5 to 107.9 MHz A .......... Australian model
[A model] ...................................................... 87.50 to 108.00 MHz
50 dB Quieting Sensitivity (IHF)
(1 kHz, 100% Mod.)
Mono .................................................................. 2.0 µV (17.3 dBf)
Stereo .................................................................. 25 µV (39.2 dBf)
Usable Sensitivity (IHF)
Mono .................................................................. 1.0 µV (11.2 dBf)
Selectivity
at 400 kHz ............................................................................ 70 dB
Signal to Noise Ratio (IHF)
RX-777
Mono / Stereo .......................................................... 76 dB / 70 dB
Harmonic Distortion
(1 kHz)
Mono / Stereo .............................................................. 0.2 / 0.3 %
Stereo Separation
1 kHz .................................................................................... 45 dB
Frequency Response
20 Hz to 15 kHz .......................................................... +0.5 / -2 dB
Antenna Input
...................................................................... 75 ohms unbalanced
3
RX-777
· DIMENSIONS
(13/16")
21.3
390.3 (15-5/16")
348 (13-11/16")
21
(13/16")
130 (5-1/8")
151 (5-15/16")
435 (17-1/8")
21
(13/16")
Unit : mm (inch)
s INTERNAL VIEW
q w e r t y u io
q MAIN (5) P.C.B.
w MAIN (2) P.C.B.
e MAIN (3) P.C.B.
r MAIN (1) P.C.B.
t INPUT (4) P.C.B.
y INPUT (1) P.C.B.
u INPUT (2) P.C.B.
i INPUT (3) P.C.B.
o OPERATION (8) P.C.B.
!0 OPERATION (1) P.C.B.
!1 OPERATION (6) P.C.B.
!2 MAIN (4) P.C.B.
RX-777
!3 OPERATION (4) P.C.B.
!4 OPERATION (5) P.C.B.
!5 OPERATION (2) P.C.B.
!6 OPERATION (3) P.C.B.
!0 !1 !2 !3 !4 !5 !6
4
RX-777
s DISASSEMBLY PROCEDURES q
Top Cover
(Remove parts in the order as numbered.) w
Disconnect the power cord from the AC outlet.
1. Removal of Top Cover
Remove 4 screws (q) and 4 screws (w) in Fig. 1.
2. Removal of Front Panel
Remove 7 knobs and 6 screws (e) in Fig. 1.
Front Panel
3. Removal of Bottom Cover
e
Remove 6 screws (r) in Fig. 1.
q
e
r
r r Bottom Cover
Fig. 1
d. Spread a cloth over the Main Chassis as shown in Fig. 2.
s OPERATION P.C.B. CHECK e. Put the OPERATION (8) P.C.B. on end as shown in Fig. 2.
f. Connect the ground point of OPERATION (8) P.C.B. to
Preparation before OPERATION P.C.B. Check
rear panel by using wire as shown in Fig. 2.
a. Remove the Top Cover.
f. Connect the ground point of OPERATION (8) P.C.B. to
b. Remove 13 screws (q) on the Rear Panel as
rear panel by using wire as shown in Fig. 2.
shown in Fig. 1.
g. Connect the J420, J421 of OPERATION (8) P.C.B. to
c. Remove 2 screws (w) on the OPERATION (8) P.C.B.
rear panel by using wire as shown in Fig. 2.
as shown in Fig. 1.
Solder the end of the wire to the ground point
of OPERATION (8) P.C.B.. (refer to P.15 D-4) Cable
Operation P.C.B. (8)
J421
J420
w
w
RX-777
Rear Panel
OPERATION (8) P.C.B.
Rear Panel
q
Fig. 2
q
q CAUTION!
Fig. 1 The ground point, J420 and J421 must be connected to
Rear Panel to keep the circuit in normal operation when
OPERATION (8) P.C.B. is removed from main chassis.
5
RX-777
s AMP ADJUSTMENTS
Confirmation of Idling Current
· Right after power is turned on, confirm that the voltages of between R111-R135 and R112-R136 are between 0.1mV and
10mV.
· If they exceed 10mV, cut R175, R176. Then reconfirm they are between 0.1mV and 10mV.
L ch R111 R112 R ch
0.1mV ~ 10.0mV 0.1mV ~ 10.0mV
(DC) (DC)
R175 R176
R135 R136
Cut off
R175 (L ch)
R176 (R ch)
Note)
· If R175 (L ch) or R176 (R ch) have already been cut off and idling current does not flow, reconnect R175 (1k) or R176 (1k).
· Q117 and Q118 are transistors for temperature correction. Apply silicone grease to the contact surface with the heat sink.
s TEST MODE
CAUTION: Before setting to the TEST mode, write down the existing preset memory content of the Tuner in a table as
shown below. (This is because setting to the TEST mode will cause the memory content to be as factory set,
i.e., all the preset memory by the user will be erased.)
Preset group P1 P2 P3 P4 P5 P6 P7 P8
A
B
C
RX-777
D
E
q Factory preset memory content
Preset group P1 P2 P3 P4 P5 P6 P7 P8
A/C/E U, C 87.5 MHz 90.1 MHz 95.1 MHz 98.1 MHz 107.9 MHz 88.1 MHz 106.1 MHz 107.9 MHz
A 87.5 MHz 90.1 MHz 95.1 MHz 98.1 MHz 108.0 MHz 88.1 MHz 106.1 MHz 108.0 MHz
B/D U, C 630 KHz 1080 KHz 1440 KHz 530 KHz 1710 KHz 900 KHz 1350 KHz 1400 KHz
A 630 KHz 1080 KHz 1440 KHz 531 KHz 1611 KHz 900 KHz 1350 KHz 1404 KHz
6
RX-777
1. Test mode for the DISPLAY to light all segments.
Turn the POWER SW ON while pressing the EDIT and
No. 8 keys simultaneously. The unit enters the TEST
mode for the DISPLAY to light all segments.
2. Test mode for the microprocessor
software version check.
While in the DISPLAY test mode, push the No. 1 key to enter
the TEST mode for the microprocessor software version
check.
3. Memory reset mode
While in the DISPLAY test mode, push the A/B/C/D/E
key to enter the Memory reset mode and all RAM
settings are reset to the factory settings.
4. Test mode to display the Protection
PS port (pin No. 80) input voltage.
Turn the POWER SW ON while pressing the EDIT and
No. 6 keys simultaneously. The unit enters the TEST
mode to display the Protection PS port input voltage as
an AD value for 3 sec.
~ Abnormal
The microprocessor will not respond to any commands
while in this mode. ~ Normal
~ Abnormal
5. Test mode to display the Protection
DC port (pin No. 79) input voltage.
Turn the POWER SW ON while pressing the EDIT and
No. 7 keys simultaneously. The unit enters the TEST
mode to display the Protection DC port input voltage as
an AD value for 3 sec.
~ Abnormal
The microprocessor will not respond to any commands
while in this mode. ~ Normal
~ Abnormal
Cancel:
When the POWER is turned OFF, the TEST mode is cancelled.
PROTECTION FUNCTION
When the microprocessor detect an abnormal condition, the Power is turned off.
Vref is the AD reference Voltage. The microprocessor compares the monitored voltage relative to Vref = 255.
PS Error Detection
PS error detection begins 1 sec. after Power ON. If the monitored level is lower than 53/255 Vref or higher than
134/255 Vref (AD value), protection is activated.
RX-777
Output DC Voltage Detection
DC voltage detection begins 4.4 sec. agter Power ON. If the monitored level is lower than 12/255 Vref or higher than
115/255 Vref (AD value), protection is activated.
Over Current Detection
Over current detection begins immediately after Power ON. If the monitored level is High, protection is activated.
7
RX-777
s DISPLAY DATA
$1 q
q V301 : 13-BT-181GK (V6994700)
PATTERN AREA
q PIN CONNECTION
Pin No. 41 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21
Connection F2 F2 NP NP 13G 12G 11G 10G 9G 8G 7G 6G 5G 4G 3G 2G 1G NX NX NX NX
Pin No. 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1
Connection P1 P2 P3 P4 P5 P6 P7 P8 P9 P10 P11 P12 P13 P14 P15 P16 NP NP F1 F1
Note : 1) F1, F2 ..... Filament 2) NP ..... No pin 3) NX ..... No extend pin 4) DL ..... Datum Line 5) 1G ~ 13G ..... Grid
q GRID ASSIGNMENT
12G 11G 10G 9G 8G 7G 6G 5G 4G 3G 2G 1G
t u t u
S4 S3 S2 S1 13G a a
j j
f f
h k b h k b
g m g m
v
r r w
e n e n
c c
p p
d d
(12G~5G, 3G, 2G) (4G)
q ANODE CONNECTION
13G 12G 11G 10G 9G 8G 7G 6G 5G 4G 3G 2G 1G
P1 a a a a a a a a a a a
P2 b b b b b b b b b b b
P3 c c c c c c c c c c c
P4 d d d d d d d d d d d
P5 e e e e e e e e e e e
P6 f f f f f f f f f f f
P7 g g g g g g g g g g g
P8 S1 h h h h h h h h h h h
RX-777
P9 j j j j j j j j j j j
P10 S2 k k k k k k k k k k k
P11 m m m m m m m m m m m
P12 S3 n n n n n n n n n n n
P13 p p p p p p p p p p p
P14 S4 r r r r r r r r r r r
P15 t, u t, u t, u t, u t, u t, u t, u t, u t, u t, u t, u
P16 w, v
8
RX-777
s IC DATA
IC301 : M38B57M6-172FP
8 bit µ-COM (Main CPU)
P20/Buz02/FLD0
P02/FLD10
P03/FLD11
P04/FLD12
P05/FLD13
P06/FLD14
P07/FLD15
P10/FLD16
P11/FLD17
P12/FLD18
P13/FLD19
P14/FLD20
P15/FLD21
P16/FLD22
P17/FLD23
P21/FLD1
P22/FLD2
P23/FLD3
P24/FLD4
P25/FLD5
P26/FLD6
P27/FLD7
P00/FLD8
P01/FLD9
64
63
62
61
60
59
58
57
56
55
54
53
52
51
50
49
48
47
46
45
44
43
42
41
P57/SRDV2/SCLK22 65 40 P30/FLD24
P56/SCLK21 66 39 P31/FLD25
P55/TxD 67 38 P32/FLD26
P54/RxD 68 37 P33/FLD27
P53/SCLK12 69 36 P34/FLD28
P52/SCLK11 70 35 P35/FLD29
P51/SOUT1 71 34 P36/FLD30
P50/SIN1 72 33 P37/FLD31
AVSS 73 32 P80/FLD32
VREF 74 31 P81/FLD33
P65/SSTB1/AN11 75 30 P82/FLD34
P64/INT4/SBUSY1/AN10 76 29 P83/FLD35
P63/AN0 77 28 VEE
P62/SRDY1/AN8 78 27 P84/FLD36
P77/AN7 79 26 P85/RTP0/FLD37
P76/AN6 80 25 P86/RTP1/FLD38
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
1
2
3
4
5
6
7
8
9
P75/AN5
P74/AN4
P73/AN3
P72/AN2
P71/AN1
P70/AN0
P61/CNTR0/CNTR2
P60/CNTR1
P47/INT2
RESET
P91/XCOUT
P90/XCIN
VSS
XIN
XOUT
VCC
P46/TSOUT
P45/T1OUT
P44/PWM1
P43/BUZ01
P42/INT3
P41/INT1
P40/INT0
P87/PWM0/FLD39
Pin No. Port I/O Function
1 P75 O /R2MU ZONE 2 OU