C-Audio ST Series User manual

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Title
Number RevisionSize
A3
Date: 1-Jul-1999 Sheet of
File:
D:\PROTEL\ST\MAINA.SCH
Drawn By:
CMOD
220p
RMOD
390k
IN4148
DMOD1
D41
IN4004
D40
IN4004
L1
CHOKE
R32
10k
R31
10k
C15
4700u
C14
4700u
D5
IN4004
D6
IN4004
FS2
T10A
FS1
T10A
+15
-15
C20
15p
C7
100u
BOTTOM
WIPERTOP
C6
100u
RV1
1k
-15
+15
C12
deleted
C13
deleted
C19
100n
C18
100n
C9
4p7
C5
4p7
C4
10p
C3
33p
C2
33p
C1
82p
R30
560R
R29
560R
R28
560R
R27
560R
R26
560R
R25
560R
R24
560R
R23
560R
R22
5k1
R21
5k1
R20
39k
R19
39k
R18
5k1
R17
5k1
R16
150R
R15
150R
R14
10k
R13
10k
R12
68k
R11
1k
R36
110k
R9
120k
R8
10k
R7
220R
R6
6k2
R5
3k3
R4
3k3
R3
10k
R2
3k3
R1
3k3
IC2
NE5534
5
67
IC1B
NE5532
3
21
8 4
IC1A
NE5532
RV2
1k
C11
100u
R10
10k
C8
10u
C10
100p
D2
IN4148
D1
IN4148
ZD1
9v1
ZD2
9v1
TR10
BC184L
TR9
BC214L
D3
IN4148
D4
IN4148
TR1
J162 TR2 J162 TR3 J162 TR4 J162
TR5
K1058 TR6
K1058 TR7 K1058 TR8 K1058
-VE A
+VE A
R35
10R R108 10R R34
10R
R33
10R
C16
47n C17 22n
RL1
D9
IN4148
+15
RLY CNTRL
OP/A
OP/A 0V
OP/A MON
C/T A
BRIDGE OUT
I/P - A
I/P + A
I/P 0V
RL4
R120
8k2
R121
8k2
C61
680p
C60
680p
C71
10p C70 10p C69 10p C68 10p
1kV
x2
SEE NOTE
SEE NOTE
2.5W
2.5W
2.5W 2.5W
2.5W
NOTE
CIRCUIT SHOWN APPLIES TO ST600
FOR ST400 TR4 & TR8 ARE NOT FITTED AND
R10 = 12k
R19 & R20 = 30k
LMB
3 4
3
C1022
ST 600/400 PCB
4
3
2
7
6
BIAS
CMRR
0dB Sensitivity Modification
Change R5 from 3k3 to 6k65
Change R6 from 6k8 to 13k

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Title
Number RevisionSize
A3
Date: 1-Jul-1999 Sheet of
File:
D:\PROTEL\ST\MAINB.SCH
Drawn By:
C64
10p
C65
10p
C66
10p
C67
10p
RL4
R123
8k2
C63
680p
C62
680p
R122
8k2
BRIDGESTEREO
L2
CHOKE
R67
10k
R68
10k
C38
4700u
C37
4700u
D14
IN4004
D15
IN4004
FS4
T10A
FS3
T10A
+15
-15
C28
15p
C27
100u
BOTTOM
WIPERTOP
C26
100u
RV3
1k
-15
+15
C35
Deleted
C36
Deleted
C33
100n
C31
100n
C30
4p7
C25
4p7
C24
10p
C23
33p
C22
33p
C21
82p
R66
560R
R65
560R
R64
560R
R63
560R
R62
560R
R61
560R
R60
560R
R59
560R
R58
5k1
R57
5k1
R56
39k
R55
39k
R54
5k1
R53
5k1
R52
150R
R51
150R
R50
10k
R49
10k
R47
68k
R48
1k
R45
120k
R44
10k
R43
220R
R42
6k2
R41
3k3
R40
3k3
R39
10k
R38
3k3
R37
3k3
IC4
NE5534
RV4
1k
C34
100u
R46
10k
C29
10u
C32
100p
D11
IN4148
D10
IN4148
ZD3
9v1
ZD4
9v1
TR20
BC184L
TR9
BC214L
D12
IN4148
D13
IN4148
TR11
J162 TR12 J162 TR13 J162 TR14 J162
TR15
K1058 TR16
K1058 TR17 K1058
TR18
K1058
-VE B
+VE B
R69
10R R109 10R R71
10R
R70
10R
C39
47n C40 22n
RL2
D18
IN4148
+15
RLY CNTRL
OP/B
OP/B 0V
OP/A MON
C/T B
I/P - B
I/P + B
I/P 0V
D42
IN4004
D43
IN4004
3
21
84
IC3A
NE5532
5
67
IC3B
NE5532
DMOD2
1N4148
RMOD
390k
CMOD
220p
BIAS
CMRR
INOUT
NOTE
CIRCUIT DIAGRAM SHOWN APPLIES TO ST600
FOR ST400 :
TR14 & TR18 ARE NOT FITTED
R46 = 12k
R55 & R56 = 30k
4
3
2
7
6
STi 600/400 PCB
C1022 3
LMB
2 4
4
8
SEE NOTE
SEE NOTE
2.5W
2.5W
2.5W
2.5W2.5W
x2
1kV
0dB Sensitivity Modification
Change R41 from 3k3 to 6k65
Change R42 from 6k8 to 13k

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Title
Number RevisionSize
A3
Date: 1-Jul-1999 Sheet of
File:
D:\PROTEL\ST\MAIN1.SCH
Drawn By:
CIRCUIT SHOWN APPLIES TO THE ST600 VERSION
FOR THE ST400 R76 = 7k5
LIVE OUTLIVE IN
SG64
PEAK B
PEAK A
OV
+15
-15
R106
3k
R107
1k5
R110
56R
C54
100u
C53
100u
C52
470u
C51
470u
D35
IN4004
D34
IN4004
D33
IN4004
D31
IN4004
Vin
2
GND 1
-15V 3
IC7
MC7915T
Vin
1
GND
2
+15V 3
IC6
MC7815T
-15
-15
ZD10
6V8
ZD9
6V8
C50
100p
C45
100p
TR22
BC214L
TR21
BC214L
+15
11
10 13
IC5D
LM339
R95
470k R96 470k
R98
470k R101 470k
R97
10M R100
10M
C47
470n C48
470n ZD7
12v
ZD8
12v
D26
IN4148
D27
IN4148
D29
IN4148
-15
-15
+15
C44
10u
D22 IN4148 D24
IN4148
D21
IN4148
D20
IN4148
ZD6
12v
ZD5
12v
C43
470n
C42
470n
R83
220k
R84
470k
R81
10M
R79
10M
R82
470k
R80
470k
R78
470k
R77
470k
-15
+15
C46
1uF
C41
1uF
D25
IN4148
D19
IN4148
R89
47k
R90
4k7 R91 1M
R94
3k
R88
3k
R75
18k
R76
11k
R74
1MR73
4k7
R72
47k
7
61
IC5B
LM339
9
814
IC5C
LM339
5
42
312
IC5A
LM339
MON A
O/P
MON B
O/P
AC 1
18V
AC 2
CON
FAN -
FAN +
POWER LED
BRIDGE SW2
BRIDGE SW1
BRIDGE LED
LED COMMON
0V
THERMAL/A
THERMAL A
RLY CONT A
RLY CONT B
o
N/C
112 C
SEE NOTE
SOFT START
/
NOTE:
STi 600 / 400 PCB
C1022 3
1 4
LMB

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Title
Number RevisionSize
A3
Date: 1-Jul-1999 Sheet of
File:
D:\PROTEL\ST\ST1000\C1048.S03
Drawn By:
C55A
1n
C54A
1n
FEEDBACK
+ MT
GT4A
SC2A
GT3A
SC1A
GT2A
ZD12A
12V
ZD13A
12V
C22A
47p
C21A
100n
R30A
100R
R31A
330R
R29A
100k
R28A
330R
R27A
100k
D14A
BAV21
D13A
BAV21
C24A
100p
C23A
100p
C33A
680p
C32A
680p
D12A
BAV21
D11A
BAV21
D22A
IN4148
D9A
IN4148
R73A
8k2
R71A
82k
R70A
82k
R67A
8k2
R72A
8k2
R69A
2k7
R68A
2k7
R66A
8k2
GND
TR19A
BC184L
TR18A
BC214L
ZD11A
12V
ZD10A
12V
D2A
IN4148
D1A
IN4148
C31A
100uF VR2A
1k
R65A
150R
R64A
150R
C30A
100uF
C29A
100uF
ZD8A
15V
ZD9A
15V
GND
GND
C14A
100uF R22A
4k7
R17A
3k3/5W
R21A
1k5
C18A
100uF
C15A
100uF
ZD7A
30V
ZD6A
15V
ZD4A
30V
ZD5A
15V
C17A
10p
R19A
330k
3
21
84
IC1A
NE5532
R23A
10k
R20A
120k
R16A
330k
R18A
680R
C13A
100uF
BOTTOM
WIPER
5
67
IC1B
NE5532 TOP
C12A
100uF
R15A
220R
C11A
4p7
RV1A
R14A
6k2
C10A
10p
C9A
33p
C8A
33p
C7A
82p
R13A
3k3
R11A
3k3
R12A
10k
R9A
3k3
R10A
3k3
SCN
BLUE
RED
GT1A
R25A
1k5
R24A
4k7
R26A
3k3/5W
C19A
100uF
- MT
R80A
30k
BRIDGE R85A
2K2
C16A
100uF
D25A
IN4148
R83A
100R
+15
-15
D26A
IN4148
R84A
100R
C52A
47p
R82A
33k
R81A
33k
C53A
680n
RV3A
220k
FEEDBACK
C1048
31
LMB
CHANNEL A DRIVER STAGE
OUT
+ MT
- MT
5

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Title
Number RevisionSize
A3
Date: 1-Jul-1999 Sheet of
File:
D:\PROTEL\ST\ST1000\C1048.S04
Drawn By:
R84B
100R
D26B
IN4148
-15
+15
R83B
100R
D25B
IN4148
FEEDBACK
+ MT
GT4B
SC2B
GT3B
SC1B
GT2B
ZD12B
12V
ZD13B
12V
C22B
47p
C21B
100n
R30B
100R
R31B
330R
R29B
100k
R28B
330R
R27B
100k
D14B
BAV21
D13B
BAV21
C24B
100p
C23B
100p
C33B
680p
C32B
680p
D12B
BAV21
D11B
BAV21
D22B
IN4148
D21B
IN4148
R73B
8k2
R71B
82k
R70B
82k
R67B
8k2
R72B
8k2
R69B
2k7
R68B
2k7
R66B
8k2
GND
TR19B
BC184L
TR18B
BC214L
ZD11B
12V
ZD10B
12V
D2B
IN4148
D1B
IN4148
C31B
100uF VR2B
1k
R65B
150R
R64B
150R
C30B
100uF
C29B
100uF
ZD8B
10V
ZD9B
10V
GND
GND
C14B
100uF R22B
4k7
R17B
4k7
R21B
1k5
C18B
100uF
C15B
100uF
ZD7B
30V
ZD6B
15V
ZD4B
30V
ZD5B
15V
C17B
10p
3
21
84
IC1A
NE5532
R23B
10k
R20B
120k
R18B
680R
C13B
100uF
BOTTOM
WIPER
5
67
IC1B
NE5532
TOP
C12B
100uF
R15B
220R
C11B
4p7
RV1B
R14B
6k2
C10B
10p
C9B
33p
C8B
33p
C7B
82p
R13B
3k3
R11B
3k3
R12B
10k
R9B
3k3
R10B
3k3
SCN
BLUE
RED
GT1B
R25B
1k5
R24B
4k7
R26B
4k7
C19B
100uF
- MT
R80B
36k
BRIDGE
C52B
47p
C16B
100u
C54B
1n
C55B
1n
R19B
330k
R16B
330k
R82B
33k
R81B
33k
C53B
680n
RV3B
220k
FEEDBACK
C1048
41
LMB
STAGE
IN
+ MT
- MT
5
CHANNEL B DRIVER

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Title
Number RevisionSize
A3
Date: 1-Jul-1999 Sheet of
File:
D:\PROTEL\ST\ST1000\C1048.S05
Drawn By:
DRAWING OF OUTPUT STAGE
COMPONENT REFERENCES SHOULD
BE SUFFIXED WITH A OR B
FOR RESPECTIVE CHANNELS
R77
2k2
R75
2k2
R47
560R
R44
560R R45 560R R46 560R
R40
560R R41 560R R42 560R R43 560R
R36
560R R37 560R R38 560R R39 560R
R32
560R R33 560R R34 560R R35 560R
G
SD
TR13
J162
G
SD
TR14
J162
G
SD
TR15
J162
G
SD
TR16
J162
G
SD
TR9
J162
G
SD
TR10
J162
G
SD
TR11
J162
G
SD
TR12
J162
TR5
K1058 TR6 K1058 TR7 K1058 TR8 K1058
TR1
K1058 TR2 K1058 TR3 K1058 TR4 K1058
C46
10P C47
10P C48 10P C49 10P
C42
10P C43 10P C44 10P C45 10P
C38
10P C39 10P C40 10P C41 10P
C34
10P C35 10P C36 10P C37 10P
D15
BYT30P400
D16
BYT30P400
R74
2K2
R76
2K2
R78
3R3
R79
3R3
C50
100n
C51
100n
C- MT
C- HT
CON
C+ HT
C+ MT
GT2
GT3
SC1
SC2
GT1
GT4
5 5
LMB
1
C1048
OUTPUT STAGE A/B
4W
4W
2.5W
2.5W
4W
4WCmod2Cmod1

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Title
Number RevisionSize
B
Date: 1-Jul-1999 Sheet of
File:
D:\PROTEL\ST\ST1000\C1048.S02
Drawn By:
ACL(B) ACL(B)
ACH(B) ACH(B)
- HT
- MT
+ MT
+ HT
RL1B
BR1B
SB5006
BR2B
SB5006
C1B
9000uF
C2B
9000uF
C3B
9000uF
C4B
9000uF
R1B
2k2
R2B
2k2
R3B
2k2
R4B
2k2
R5B
10R R6B
10R
R8B
10R
R7B
10R
L1B
C5B
220n
C6B
100nC6A
100nC5A
220n
L1A
R7A
10R
R8A
10RR6A
10R
R5A
10R
R4A
2k2
R3A
2k2
R2A
2k2
R1A
2k2
C4A
9000uF
C3A
9000uF
C2A
9000uF
C1A
9000uF
BR2A
SB5006
BR1A
SB5006 RL1A
+ HT
+ MT
- MT
- HT
ACH(A)ACH(A)
ACL(A)ACL(A)
5
400V
400V
2.5W
2.5W
2.5W
2.5W
GND GND
OUTPUT B
C1048
POWER SUPPLY SECTION
1
2
LMB
OUTPUT A
GNDGND
2.5W
2.5W 2.5W 2.5W
400V 400V
FEEDBACK FEEDBACK

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Title
Number RevisionSize
A3
Date: 1-Jul-1999 Sheet of
File:
D:\PROTEL\ST\ST1000\C1048.S01
Drawn By:
7
61
IC1B
LM339
D6B
IN4148
D6A
IN4148
+15
+15
21
RL1B
RELAY
21
RL1A
RELAY
THERMAL A
THERMAL/A
LED COMMON
CN1.4
BRIDGE LED
CN1.5
BRIDGE SW1
BRIDGE SW2
POWER LED
CN1.3
FAN +
FAN -
AC 2
CON
AC 1
18V
CHAN A
OUTPUT
5
42
312
IC1A
LM339
R48A
47k
R49A
4k7
R50A
1M
R51B
11k
R55B
18k
R52A
3k
D1A
IN4148
C25A
1uF
+15
-15
R53A
47k
R54A
47k
R58A
470k R59A 470k
R57A
10M R60A
10M
R61B
470kR56A
220k
C26A
100u ZD1A
12v
ZD2A
12v
D2A
IN4148
D3A
IN4148
D5A
IN4148 D4A
IN4148
C27B
10u
+15
-15
TR17A
BC214L
C28A
100p
ZD3A
6V8
-15
Vin
1
GND
2
+15V 3
IC2
MC7815T
Vin
2
GND 1
-15V 3
IC3
MC7915T
D1
IN4004
D2
IN4004
D3
IN4004
D4
IN4004
C1
470u
C2
470u
C3
100u
C4
100u
R3
56R
R1
1k5
R2
3k
-15
+15
OV
PEAK A
CN1.1
NTC1
SG64
LIVE IN LIVE OUT
PEAK B
CN1.2
-15
ZD3B
6V8
C28B
100p
TR17B
BC214L
-15
D4B
IN4148
D3B
IN4148
D2B
IN4148
ZD2B
12v
ZD1B
12v
C26B
100u
R60B
10M
R57B
10M
R59B
470k
R58B
470k
R54B
47k
R53B
47k
C25B
1uF
D1B
IN4148
R52B
3k
R50B
1M
R49B
4k7
R48B
47k
CHAN B
OUTPUT
9
814
IC1C
LM339
11
10 13
IC1D
LM339
+15
NTC2
SG64
+ MT
- MT
+ MT
- MT
LMB
51
1
C1048
ST1000 PROTECTION
/
SOFT START
112 C
N/C
o
/
(Y29)
(Y30)
(Y31)
CHANNEL B
CHANNEL A

ST Series Modification Procedure
General
The following changes are to be made to All ST amplifiers irrespective of Issue :
1) Remove C20 & C28 (10pF) from the PCB and replace with 15pF, 50V ceramic capacitors.
2) Remove C10 & C32 (47pF) from the PCB and replace with 100pF, 50V ceramic
capacitors.
3) Remove C17 & C40 (100nF) from the PCB and replace with 22nF, 250V polyester
capacitors.
4) Remove C16 & C39 (220nF) from the PCB and replace with 47nF, 250V polyester
capacitors.
5) Remove C12, C13, C35 & C36 from the PCB. Note, It is better to do this by cutting the
component leads close to the PCB to avoid damaging PCB traces.
6) Fit 2 x 1N4148 diodes solder-side in reverse parallel from IC2 pin 3 to 0V, as per figure 1.
7) Fit 2 x 1N4148 diodes solder-side in reverse parallel from IC4 pin 3 to 0V, as per figure 1.
8) Remove any capacitors fitted on the solder-side of the PCB that connect to the middle pin
of the Output transistors. DO NOT remove the 10pF capacitors fitted across the two
outside pins of the K1058 transistors.
9) Fit 220pF, 1kV ceramic capacitors between Drain and Source of TR6 and TR17 as per
figure 1.
Issue Specific Changes
At this point, it is necessary to ascertain the exact issue status of the unit before proceeding,
as follows:
1) Issue 6 PCBs: Go To Procedure 1.
2) Issue 4 & 5 PCBs fitted with P1040 & P1041 protection daughter boards: Go To
Procedure 2.
3) Issue 4 & 5 PCBs fitted with Resistor-Resistor-Diode-Capacitor networks in positions R55,
R56, R19 and R20: Go To Procedure 3.
4) Previous Issues: Go To Procedure 4.

Procedure 1 Issue 6 PCBs
1) Remove R17, R22, R53 & R58 (5k6) from the PCB and replace with 5k1, 1/4W.
2) Remove R18, R21, R54 & R57 (1k8) from the PCB and replace with 5k1, 1/4W.
3) Remove ZD1, ZD2, ZD3 & ZD4 (12V) from the PCB and replace with 9V1 1/2W.
4) Fit 390k, 1/4W resistor solder-side between D40 Cathode and D41 Anode, as per figure 2.
5) Fit 390k, 1/4W resistor solder-side between D43 Cathode and D42 Anode, as per figure 2.

Procedure 2 Issue 4 & 5 PCBs with Modification Daughter Boards
1) Remove R17, R22, R53 & R58 (5k6) from the PCB and replace with 5k1, 1/4W.
2) Remove ZD1, ZD2 & ZD3 (12V) from the PCB and replace with 9V1 1/2W.
3) Fit 9V1, 1/2W zener diode solder-side in position ZD4 as per figure 3.
Modification to P1040 Daughter Board
1) Remove R18 & R21 (1k8) from the PCB and replace with 5k1, 1/4W.
2) Fit 390k, 1/4W resistor solder-side between D1 Cathode and D2 Anode, as per figure 4.
Modification to P1041 Daughter Board
1) Remove R54 & R57 (1k8) from the PCB and replace with 5k1, 1/4W.
2) Fit 390k, 1/4W resistor solder-side between D2 Cathode and D1 Anode, as per figure 4.
Figure 4
Procedure 3 Issue 4 & 5 PCBs with Resistor-Resistor-Diode-Capacitor Networks

1) Remove R17, R22, R53 & R58 (5k6) from the PCB and replace with 5k1, 1/4W.
2) Remove R18, R21, R54 & R57 (1k8) from the PCB and replace with 5k1, 1/4W.
3) Remove ZD1, ZD2, ZD3 & ZD4 (12V) from the PCB and replace with 9V1 1/2W.
4) Fit 390k, 1/4W resistor between Component Network diodes as per figure 5.
5) Fit 390k, 1/4W resistor between Component Network diodes as per figure 5.
Figure 5
Procedure 4

1) Remove R17, R22, R53 & R58 (5k6) from the PCB and replace with 5k1, 1/4W.
2) Remove R18, R21, R54 & R57 (1k8) from the PCB and replace with 5k1, 1/4W.
3) Remove ZD1, ZD2, ZD3 & ZD4 (12V) from the PCB and replace with 9V1 1/2W.
4) Remove Components fitted in positions R19, R20, R55 & R56 and replace with networks
consisting of 1N4004 diodes, 8k2 resistors, 39k resistors, 680pF capacitors and 390k
resistors as per figure 6.
5) Remove the fixing screws for the K1058 output transistors and remove the insulating pad
between the transistor and the heatsink.
6) Rub-down the heatsink with medium abrasive paper to remove any burrs or remnants of
insulating pad.
7) Ensure the mounting faces of the power transistors are clean and then apply a thin, even
layer of heatsink compound to the device and re-assemble the devices onto the heatsink.
Ensure the fixing screws are secure but take care not to over-tighten.
Figure 6
General notes

Once the appropriate modifications have been carried out it is recommended that the
following checks are performed before attempting to re-test the amplifier.
1) Output Stage : Check for faulty Output transistors in the following way :
a) Measure between Drain and Source of each transistor with a multi-meter set on a low
Ohms range. A short-circuit reading indicates one or more transistors is faulty.
b) Measure between Gate and Source of each transistor with a multi-meter set on the 2k
Ohms range. A reading of less than 560 Ohms indicates a faulty transistor.
2) Zobel Resistors : Check R34, R35, R106, R69, R71 & R109. Replace with the correct
10R, 2.5W parts if faulty, or show any signs of having over-heated.
Final Checks
Once the amplifier has been modified and repaired it is always possible that there remains
one or more components which have been weakened or damaged by any previous failure.
The easiest way to confirm all is well is to perform a simple short-circuit test on the amplifier
as follows : Drive the amplifier into a 4 Ohm load to an output level just prior to the clip point.
Connect a short circuit across the amplifier output for a period of approximately ten seconds.
Remove the short circuit and check the output returns to its previous level. If any Output
transistors fail during this test, they should be replaced, but output transistors continue to fail
(especially if they are recently replaced parts) the current limiting protection circuits should be
checked for faulty components.