TX-8255
SERVICE MANUAL
SERVICE MANUAL
RC-666S
STEREO RECEIVER
MODEL
TX-8255
Ref. No. 4088
062008
Black and Silver models
120V AC, 60Hz
230 - 240V AC, 50Hz
B MDC
B MPP, S MPP
SAFETY-RELATED COMPONENT
WARNING!!
COMPONENTS IDENTIFIED BY MARK
ON THE
SCHEMATIC DIAGRAM AND IN THE PARTS LIST ARE
CRITICAL FOR RISK OF FIRE AND ELECTRIC SHOCK.
REPLACE THESE COMPONENTS WITH ONKYO
PARTS WHOSE PART NUMBERS APPEAR AS SHOWN
IN THIS MANUAL.
MAKE LEAKAGE-CURRENT OR RESISTANCE
MEASUREMENTS TO DETERMINE THAT EXPOSED
PARTS ARE ACCEPTABLY INSULATED FROM THE
SUPPLY CIRCUIT BEFORE RETURNING THE
APPLIANCE TO THE CUSTOMER.
TX-8255
EXPLODED VIEW
TX-8255
A043
x 3 pcs.
A017
x 5 pcs.
A041
x 2 pcs.
A015
x 11 pcs.
A037
x 2 pcs.
A301
x 2 pcs.
A029
x 3 pcs.
E801
x 2 pcs.
A035
x 2 pcs.
A019
x 4 pcs.
E801
x 5 pcs.
A035
x 2 pcs.
A217
x 2 pcs.
A205
x 20 pcs.
P501a
x 8 pcs.
A025
x 3 pcs.
A025
x 3 pcs.
A031
x 5 pcs.
A035
x 2 pcs.
A035
x 2 pcs.
A203
x 6 pcs.
A521a
x 4 pcs.
A023
x 3 pcs.
A009
x 4 pcs.
A011
x 4 pcs.
A213
x 3 pcs.
A039
A212
A204
A013
A216
A211
A201
P715
P704
P901
U10
U07
U02
U09
T901
U06
U05
U12
U13
U01
U08
U03
U04
A214
A001
A003
F902
F901
D911
Q521
Q524
Q522
Q523
F903
A021
A209
A027
A033
A208
A207
A202
A210
A007
A005
A045
A215
A219
A204
A216 ---> <DC> Type only
TX-8255
BLOCK DIAGRAM
TX-8255
SPA
SPB
THERM
PRO
-B1
E
+B1
UP
DOWN
STB
DATA
CL
TUNL
FLAC2
FLAC1
-VP
MUT
REMIN
FLDRST
FLDCS
FLDCLK
FLDSDO
+B3
-B3
TMUT
PLLCLK
PLLSDO
STEREO
SD
RDSCLK
RDSDAT
POW
+5.6V
+5V_MPU
+5V_CPU
+5V_CPU
+12V
-12V
TU-L
RI
IRIN
IROUT
K0
K1
K2
KEYINT0
KETINT1
KEYINT2
K3
KEYINT3
LEDSTBY
FLAC1
FLAC2
+5.6V
Q525, 526
Q581, 582
PROTECT
TO POWER AMP
120V
PRIMARY
THERMAL
SENSOR
Q855
VOLTAGE REGURATOR
VOLTAGE
REGURATOR
Q901
PHONO EQULIZER
Q301
PHONO
OUT
IN
TAPE 1
CD
PLAY1
V1
LINE 1 IN
V2REC
V2PLAY
TUNER
PLAY2
REC2
OUT
IN
TAPE 2
LINE 2 IN
AUDIO
IN
/
OUT
MOTOR DRIVE
Q481
DISPLAY CONTROL
MICROPROCESSOR
Q701
FL DRIVER
Q851
FL DISPLAY
Q852
FM/AM(RDS) TUNER UNIT
CONTROL KEYS
TO
SELECTOR
&
PHONO
EQ
.
Q302
PHONO
CD
REC1
SELECTOR
240V
W-TYPE ONLY
Q591
RELAY
DRIVE
Q592
RELAY
DRIVE
POWER AMP.
RL901
PRI. RELAY
F903
OUTLET
AC IN
P501
SPEAKERS
A
SPEAKERS
B
RL591
SP. A RELAY
RL592
SP. B RELAY
P503
PHONES
C916
D911
Q921
Q922
D920
F901
Q912
R641
VOLUME
Q491
MUTING
R393
BALANCE
F902
D920
T902
SUB TRANS.
C915
REMOTE SENSOR
RI
IR IN
IR OUT
STANDBY
Q402
R409
BASS
Q401
R415
TREBLE
S901
W TYPE ONLY
THERMAL
FUSE
T901
Q706
D915 - 918
MAIN TRANS.
+12V
-12V
M30622MWP
U851
M66005
A
1
2
3
4
5
B
C
DE
FG
H
TX-8255
BLOCK DIAGRAM
TX-8255
SPA
SPB
THERM
PRO
-B1
E
+B1
UP
DOWN
STB
DATA
CL
TUNL
FLAC2
FLAC1
-VP
MUT
REMIN
FLDRST
FLDCS
FLDCLK
FLDSDO
+B3
-B3
TMUT
PLLCLK
PLLSDO
STEREO
SD
RDSCLK
RDSDAT
POW
+5.6V
+5V_MPU
+5V_CPU
+5V_CPU
+12V
-12V
TU-L
RI
IRIN
IROUT
K0
K1
K2
KEYINT0
KETINT1
KEYINT2
K3
KEYINT3
LEDSTBY
FLAC1
FLAC2
+5.6V
Q525, 526
Q581, 582
PROTECT
TO POWER AMP
120V
PRIMARY
THERMAL
SENSOR
Q855
VOLTAGE REGURATOR
VOLTAGE
REGURATOR
Q901
PHONO EQULIZER
Q301
PHONO
OUT
IN
TAPE 1
CD
PLAY1
V1
LINE 1 IN
V2REC
V2PLAY
TUNER
PLAY2
REC2
OUT
IN
TAPE 2
LINE 2 IN
AUDIO
IN
/
OUT
MOTOR DRIVE
Q481
DISPLAY CONTROL
MICROPROCESSOR
Q701
FL DRIVER
Q851
FL DISPLAY
Q852
FM/AM(RDS) TUNER UNIT
CONTROL KEYS
TO
SELECTOR
&
PHONO
EQ
.
Q302
PHONO
CD
REC1
SELECTOR
240V
W-TYPE ONLY
Q591
RELAY
DRIVE
Q592
RELAY
DRIVE
POWER AMP.
RL901
PRI. RELAY
F903
OUTLET
AC IN
P501
SPEAKERS
A
SPEAKERS
B
RL591
SP. A RELAY
RL592
SP. B RELAY
P503
PHONES
C916
D911
Q921
Q922
D920
F901
Q912
R641
VOLUME
Q491
MUTING
R393
BALANCE
F902
D920
T902
SUB TRANS.
C915
REMOTE SENSOR
RI
IR IN
IR OUT
STANDBY
Q402
R409
BASS
Q401
R415
TREBLE
S901
W TYPE ONLY
THERMAL
FUSE
T901
Q706
D915 - 918
MAIN TRANS.
+12V
-12V
M30622MWP
U851
M66005
A
1
2
3
4
5
B
C
DE
FG
H
TX-8255
SCHEMATIC DIAGRAMS-1
AMPLIFIER SECTION
TX-8255
DATA
CLK
POFF2
TU_L
TU_R
SE1H
PROTECT
PROTECT
STB
VOL_UP
SP_A
SP_B
SP_A
SP_B
DIRECT
+12VA
DIRECT
VOL_DN
AMUT
MON-A
MON-B
+12VA
5.6V
-12VA
VOL_DN
VOL_UP
STB
AMUT
DATA
MON-A
+12VS
MON-B
+12VR
CLK
+10S
FLAC2
FLAC1
FLAC1
FLAC2
-VP
SE1H
L2
R2
E
R3
E
E
L3
MTR+
MTR-
MTRG
R
L
R
L
L
VIDEO
TREBLE
BASS
VS
NC
OUT1
VREF
IN1
GND
MOTOR DRIVE
BALANCE
PHONO
EQUALIZER
SEL
STB
DATA
CL
GND
T2 REC
T2 PLAY
VSS
VDD
PHONO
CD
T1 PLAY
DVD
V REC
V PLAY
TUNER
PHONO
L
R
R
L
R
L
CD
OUT
TAPE 1
IN
TAPE 2
R
L
R
L
R
L
RLGND
T1 REC
P918
BUS
RLGND
+12V
-12V
TU_GND
TS_GND
SPEAKERS
R
LL
R
AB
IN2
OUT2
VCC
IN
LINE 1 IN
LINE-2 IN
R
V_GND
RLGND
MPUGND
RL1N4003
1SR139-100
D915,D921:
GP104003E
NC
NAAF-8886
MPUGND
To NADG-8876
SD-2 : G3
MICROPROCESSOR PCB
NC
D401-D404 :
1SS133 or 1SS270
Q401-Q402 : NJM2068L-D
C915, 916 :
8200/56
NC
ID+
ID-
2SC5197
2SA1940
[0.6V]
[-0.6V]
[-0.6V]
[-55.8V]
[-22.8V]
[55.8V]
[55.8V]
[56.3V]
[56.3V]
[-55.7V]
[0.6V]
-O
ID+
ID-
2SC5197
2SA1940
[0.6V]
[-0.6V]
[-0.6V]
[-55.8V]
[-22.8V]
[55.8V]
[55.8V]
[56.3V]
[56.3V]
[-55.7V]
[0.6V]
-O
NAPS-8889
8A/125V
NAPS-8887
VOLUME
NAAF-8888
R413
100K
C424
223Z
R311
39K
R313
100K
R314
100K
R417
1K
R418
1K
R575
220K
C342
223Z
R335
330
R336
330
R337
1M
R338
1M
R344
330
R345
1M
R346
1M
R302
1K
R349
22K
R343
330
R435
220K
R301
1K
C313
10/50
R304
56K
R303
56K
R305
220K
R306
220K
C307
100/10
R312
39K
C312
182J
Q301:B
NJM4565D-X
6
5
7
Q301:A
NJM4565D-X
3
2
8
1
4
C314
10/50
C345
223Z
R350
22K
C308
100/10
R318
1M
R317
1M
R316
330
R322
1M
R321
1M
R319
2.2K
R324
330
R326
1M
R325
1M
R323
330
R330
1M
R329
1M
R327
2.2K
R328
2.2K
R331
330
R332
330
R333
1M
R334
1M
R407
3.3K
C311
182J
C301
471K
C302
471K
C309
682J
C310
682J
R307
820
R308
820
R309
470K
R310
470K
R401
1K
C421
223J
C422
223J
C403
47/25
C407
47/25
R404
220K
R405
22K
R406
22K
C392
101K
C391
101K
C404
47/25
R391
1K
C416
220/16
C971
223Z
R951
(1/2W)
2.2
C928
100/50
C931 223Z
R491 47K
R492 47K
R436
2.2K
D952
1SS133
Q302
TC9273CNG-010
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
C423
223Z
C443
NC
R442
10
C401
47/25
R441
10
R461
100K
R462
100K
R451
3.3K
R459
3.3K
R460
3.3K
R452
3.3K
D450
P916B
D981
NC
D982
NC
Q492
RN1241-A
Q592
DTC123JS
Q591
DTC123JS
R411
1.2K
R595
10(1/2W)
C402
47/25
R402
1K
R408
3.3K
C408
47/25
R392
1K
R599
390(1W)
R598
390(1W)
R457
3.3K
C455
47/25
C435
NC
Q402:A
3
2
8
1
4
Q491
RN1241-A
C456
47/25
R458
3.3K
C428
NC
C429
NC
Q401:B
6
5
7
Q401:A
3
2
8
1
4
R403
220K
P301
P302
D983
C981
NC
C591
103J
C592
103J
D591
D592
RL592
5
2
1
6
3
4
P501
R414
100K
C442
4.7/50
C436
NC
R315
330
R320
2.2K
C319
NC
C320
NC
C323
NC
C324
NC
P915B
P917A
NC
C341
223Z
J594
NC
P917C
NC
R952
(1/2W)
2.2
P917D
NC
J593
D951
NC
J591
J592
Q925
NC
C433
103J
C434
103J
C412
47/25
R412
1.2K
C411
47/25
P914B
RL450
RL921
C343
223Z
J596
NC
R339
330
R340
330
R341
1M
C329
LIST
R342
1M
C330
LIST
P303
C459
103J
C953
4.7/50
+
RL922
R925
10(1/2W)
JL261B
1
2
3
4
D921
RL1N4003
GP104003E
D922
MTZJ33D
Q924
2SA965-Y
D954
MTZJ4.7B
Q493
KRA102M
D491
1SS133
C941
10/50
J103
R953
100K
J101
C925
334J
C919
330/35
C918
1000/35
C918A
NC
J902
NC
J900
NC
R903
NC
C912
334J/50V
C911
334J/50V
P917B
NC
C305
152J
C306
152J
C303
47/25
C304
47/25
C441
100/16
R924
560(1/2W)
R455
22K
R456
22K
C415
220/16
C527
47/63
C528
47/63
J102
C534
102J
C532
102J
C531
102J
C533
102J
C535
102J
C536
102J
Q452
DTC123JS
C426
NC
C425
NC
E591
E592
D953
1SS133
E593
NC
C930
223Z
R932
330K
R934
100(1/2W)
R594
(1/2W)
2.2
R573
10K
R572
22K
C582
223Z
Q583
2SA970
R574
47K
R593
(1/2W)
2.2
R571
33K
Q581
2SC2240
Q582
2SC2240
C526
NC
+
C526A
NC
+
C315
220/16
C316
220/16
R352
10
R351
10
R353
10
R354
10
C353
22/50
C354
22/50
JL913B
D571
MTZJ5.1B
C583
1/50
C317
LIST
C318
LIST
C321
LIST
C322
LIST
C325
LIST
C326
LIST
C327
LIST
C328
LIST
C331
C332
C405
101K
C406
101K
C409
LIST
C410
LIST
Q403:A
Q403 : NJM2068L-D
3
2
8
1
4
C453
101K
Q403:B
6
57
C454
101K
C457
101K#
C458
101K#
C581
100/16
Q481
TA7291SG
1
2
3
4
5
6
7
8
9
RL591
4
3
61
2
5
R931
3.3K
(1/4W)
R933
22(1/2W)
R904
NC
R905
NC
R901
NC
R900
NC
Q922
79M12
3
O
2
I
1
G
C923
10/50
C922
33/50
C921
223Z
C920
223Z
J901
C926
100/50
J595
NC
J903
P702B
1
2
3
4
5
6
7
8
9
10
11
12
13
P701B
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
JL716B
TO_NADIS-8887
SD-3 : C2
1
2
3
JL711B
3
2
1
R906
NC
JL613A
P705B
1
34
2
P704B
1
34
2
C915
C916
C924
334J
D911
D10XB60H
1
3
4
2
R415
100K
2
6
5
3
9
4
8
1
7
R393
250K
4
1
9
2
8
3
R409
100K
8
4
9
5
3
6
2
1
7
Q921
78M12
3
O
2
G
1
I
R919
1(1/2W)
D918A
D918
D3SBA20
Q921A
HEATSINK
4
31
2
R935
D924
GP104003E
RL1N4003
D986
NC
C983
NC
D984
C982
222J
D985
NC
Q402:B
6
5
7
JL918B
D920
RL1N4003
GP104003E
C525
NC
+
C525A
NC
+
R419 3.3K
R420 3.3K
C418
47/25
C451
47/25
C452
47/25
R454
220K
R453
220K
C461
47/25
C462
47/25
C417
47/25
R501
470
R565 120K
C501
47/50
+
R507
47
R509
47
C519
104J
R519
1K
R517
1K
R521
(1/2W)
82
R577 120K
R563 100K
D511
1SS133
R561
270
C503
101K
R503
27K
Q507
Q531
R581
5.6K
R583
3.9K
R587
2K
R589
3.3K
Q533
R567
22
C509
10/50
+
R579
100
C511
NC
Q503
R531
18K
R525
(1/2W)
68
R527
(1/2W)
82
C521 10/50
+
Q513
Q515
R547
0.22(5W)
C515 101K
R515
1.5K
C505
220/25
+
C597
NC
C523
020C
Q509
C507
NC
R569
22
R545
22K
L501
J691
NC
R555
(1W)
8.2
C517 473J
P597A
NC
P597B
NC
C513
47/25
+
P511
R535 18K
C595
NC
C529
NC
R513
56K
R533
56K
R543
(1/2W)
220
R541
(1/2W)
2.2
R539
(1/2W)
2.2
R591
(1/4W)
2.2
Q501
R505
10
Q529
BL
2SC2458-GR
R549
3.3K
R585 820
Q519
2SA1930
Q517
2SC5171
Q523
R511
5.6K
Q505
Q505, 506 : 2SC2240-GR, -BL
R523
(1/2W)
82
R553
47K
Q527
2SC2229-Y
R551
33K
R529
(1/2W)
47
R502
470
R566
120K
C502
47/50
+
R508
47
R510
47
C520
104J
R520
1K
R518
1K
R522
(1/2W)
82
R578
120K
R564 100K
D512
1SS133
R562
270
C504
101K
R504
27K
Q508
Q532
R582
5.6K
R584
3.9K
R588
2K
R590
3.3K
Q534
R568
22
C510
10/50
+
R580
100
C512
NC
Q504
R532
18K
R526
(1/2W)
68
R528
(1/2W)
82
C522
10/50
+
Q514
Q516
R548
0.22(5W)
C516 101K
R516
1.5K
C506
220/25
+
C598 NC
C524
020C
Q510
C508
NC
R570
22
R546
22K
L502
J692
NC
R556
(1W)
8.2
C518 473J
P598A
NC
P598B
NC
C514
47/25
+
P512
R536 18K
C596
NC
C530
NC
R514
56K
R534
56K
R544
(1/2W)
220
R542
(1/2W)
2.2
R540
(1/2W)
2.2
R592
(1/4W)
2.2
Q502
R506
10
Q530
BL
2SC2458-GR
R550
3.3K
R586 820
Q520
2SA1930
Q518
2SC5171
Q522
Q524
R512
5.6K
Q506
R524
(1/2W)
82
R554
47K
Q528
2SC2229-Y
R552
33K
R530
(1/2W)
47
JL917B
F912
J912
J911
F911
JL918A
D912
D10XB60H
P919
R921
0.47(1/2W)
P915A
P916A
P914A
8
9
10
11
12
13
14
16
15
18
17
JL917A
C991
104J
R922 0.47(1/2W)
J991
J992
C992
104J
R923
5.6(1/2W)
C995
NC
JL913A
C993
NC
C994
NC
F913
4A125V (NC)
F914
4A125V (NC)
R644
8.2K
R643
8.2K
C648
223Z
P641
WS-CLAMP
P642
WS-CLAMP
JL613B
R641
47
1
5
2
6
3
Refer to following table about the parts displayed by mark "LIST".
<Note>
NC = No mount of parts.
SD-Z : XY
Location of connected terminal in schematic diagrams.
SD-Z = Schematic diagrams-Z. X = A to H, Y = 1 to 5.
To POWER TRANS.
SD-4 : E1
THE COMPONENTS IDENTIFIED BY MARK
ARE CRITICAL FOR SAFETY
REPLACE ONLY WITH PART NUMBER SPECIFIED.
VOLTAGE (MEASURED WITH VOLTMETER)
IS DC VOLTAGE.(NO INPUT SIGNAL).
ALL PNP TRANSISTORS ARE EQUIVALENT TO 2SA1015-GR UNLESS OTHERWISE NOTED.
ALL NPN TRANSISTORS ARE EQUIVALENT TO 2SC1815-GR UNLESS OTHERWISE NOTED.
ALL DIODES ARE EQUIVALENT TO 1SS133 UNLESS OTHERWISE NOTED.
ELECTROLYTIC CAPACITORS (
) ARE IN uF/WV.
ALL CAPACITORS ARE IN pF/50WV UNLESS OTHERWISE NOTED.
EX) 030- 3pF 330- 33pF 331- 330pF 333- 0.033uF
ALL RESISTORS ARE IN OHMS 1/4WATTS UNLESS OTHERWISE NOTED.
THE THICK LINES ON PC BOARD ARE THE PRINTING SIDE OF THE PARTS.
EX)
PRINTING SIDE
CIRCUIT IS SUBJECT TO CHANGE FOR IMPROVEMENT.
!
NOTE
POWER AMP. L ch
POWER AMP. R ch
U08
AMPLIFIER PC BOARD
U09
TRANS. SEC.
TERMINAL PC BOARD
U10
VOLUME PC BOARD
SELECTOR
NC
Q501-504 : 2SC2240-BL
Q507 - 510, 513, 514 : 2SA949-Y
Q515, 516 : 2SC2229-Y
Q531 - 534 : 2SC1740S-S
R587 :
IDLING ADJUST
R588 :
IDLING ADJUST
Q521
OUT
IN
DISPLAY PCB
NC
NC
NC
U07
HEADPHONE JACK
PC BOARD
NAETC-8882
P503
PHONES
3
2
1
C876
104Z
C874
102J
C875 102J
L855
220M
L853
220M
L854
220M
P504
JL711A
3
2
1
+12V
-12V
+57.6V
+57.6V
-57.6V
-57.6V
0V
0V
+1.2V
+1.2V
-1.2V
-1.2V
-12V
+12V
C317, 318
C321,322,
C325-330
C409, 410
None
101K
MDC
MPP
TYPE --->
A
1
2
3
4
5
B
C
DE
FG
H