39
11. Troubleshooting Driver Amplifier & Bias Network Circuits
Troubleshooting Driver Amplifier & Bias Network Circuits
BIAS
NETWORK
FB
OUT
T
RE
OUTPUT
(-)
(+)
FIGURE 11-1 - PROTECTION MODE
10/30/
11.1A124
1
2
4
5
6
7
8
3
9
VC
C
VS
S
+V
E
O
U
T
-V
E
O
U
T
IC601
STK350-230
HF
IN
PU
T
(+)
(-)
-57.5
1.
1
-1
54.4
C606
R
605 470
C
603
54.3
C604
R604 68
R
603
330
R
602 68
C605
47
16V
+
C602
100
FB
-0
.1
-0
.1
+
C601
10
50V
R601
1
IN
2
3
4
6
7
8
9
1
TR3
TR2
TR1
R1
R2
TR4
5
R9
R4
TR5
D1
R5
D2
TR8
R8
R7
D4
D3
R3
TR7
TR8
R5
INPUT
NF
-VEOUT
+VEOUT
V55
GNO
VCC
IC601 STK350-230
Protection light will not go off after replacing Output transistors
Most modern Power Amplifiers use an IC package for the Drive Amplifier (shown in Figure 11-1). If you have
small DC offset voltages at the Driver amplifier output, the protection circuit will be triggered and the receiver will
enter the protection mode. In this case, change the Driver amplifier IC. If that does not solve the problem, check
the positive and negative power supplies to the Driver amplifier IC. Sometimes there are switching networks in
the B+ and B- paths to the Driver amplifier IC. These switching networks are used to limit the gain of the Driver
amplifier.
NOTE: Small offset voltages on multiple channels are usually caused by bad ground connections (troubleshoot
for open ground trace or traces).
Содержание STR-DE845
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