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Tait T858 User Manual
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M850-00
T858/859 Fault Finding
D4.9
Copyright TEL
31/09/98
4.6.2
T858 P
ower Contr
ol
Appr
oximate voltages under no
rmal operating condi
tions:
Measur
ement
Output Power
20W
50W
forwar
d power at "FWD-PWR" pad (beside IC3
)
R
V63/R64 (R
V63 wiper)
2.5V
1.4V
4V
2.1V
Does power control work?
Check 12V DC present
on IC1 pin 14.
Check sense volta
g
es
from directional coupler.
Check IC3 pins 7 & 1.
Check Q10 & Q11.
Check IC1 pin 1 >12V DC
when forward power low.
Does forward power
alarm output work?
Does reverse power
alarm output work?
Check Q12 & Q13.
Check IC1 pin 7 >12V DC
when reverse power hi
g
h.
Heat R72 with tip
of solderin
g
iron.
Power control OK.
N
N
N
Y
Y
Y
Y
Heat R72 with tip
of solderin
g
iron.
Check IC1 pin 13 is 0 to 1.4V
as set by RV69.
Check IC1 pin 14
g
oes from
hi
g
h to low as R72 heats up.
Check D17.
Does temperature
shutdown circuit
turn down output power?
N
272
274
Table of Contents
Part a Introduction to Servicing
13
Default Chapter
13
Table of Contents
13
1 General
15
Additional Technical Information
15
Caution: CMOS Devices
15
Caution: Aerial Load
16
Caution: Beryllium Oxide & Power Transistors
16
2 Mechanical
17
Torx Recess Head Screws
17
Pozidriv & Philips Recess Head Screws
18
Disassembly/Reassembly
19
Receivers/Exciters/Transmitters
19
Power Amplifiers
19
Cover Screw Torques
19
3 Component Replacement
21
Leaded Components
21
Desoldering Iron Method
21
Component Cutting Method
21
Surface Mount Devices
22
Cased Mica Capacitors
22
4 Software History
23
Pgm800Win V1.0
23
Pgm800Win V2.00
23
T855 General Information
27
T855 General Information
29
Introduction
31
Specifications
32
Introduction
32
General
33
RF Section
33
Audio Section
35
General
35
Ctcss
35
Mute Operation
36
Microprocessor Controller
36
Test Standards
36
European Telecommunication Standard (ETS)
36
DTI CEPT Recommendation T
37
Telecommunications Industry Association
37
Product Codes
38
Standard Product Range
39
T855 Circuit Operation
41
Introduction
43
T855 Circuit Operation
43
Receiver Front End
44
IF Circuitry
45
Mixer
45
Carrier Mute
46
Noise Mute (Squelch)
46
Audio Processor
47
Power Supply and Regulators
48
Microcontroller
49
Synthesised Local Oscillator
50
Vco
51
Received Signal Strength Indicator (RSSI)
52
Title
54
Audio Processor Links
60
General
60
Audio Processor Linking Details for CTCSS
61
Alignment of Receiver Front End and if
62
Synthesiser Alignment
62
Carrier Level Mute
64
Gating Delay
64
Noise Mute Adjustment
64
Audio Processor
65
Line Amplifier Output
65
Monitor Amplifier Output (Speaker Output)
65
Ctcss
65
Decoder Operation
65
Opening Sinad
65
High Pass Filter
66
Rssi
66
T855 Functional Testing
67
Figure
67
Current Consumption
69
Sensitivity
69
Switching Range
69
Audio Distortion
70
Ultimate Signal-To-Noise Ratio
70
De-Emphasised Audio Frequency Response
71
Noise Mute (if Linked In)
72
RSSI (if Fitted)
72
Carrier Level Mute (RSSI Fitted & Carrier Mute Linked In)
73
Title
76
Pgm800Win Generated Errors
82
Fault Finding Charts
83
Microcontroller (IC810)
83
Basic Checks
83
Serial Communication
84
CTCSS Decode
85
Regulator
86
Synthesiser
87
Noise Mute
90
Carrier Mute
91
Receiver
92
Audio
93
T856/857 General Information
125
Introduction
131
Specifications
132
Introduction
132
General
132
RF Section
133
Audio Processor
134
Inputs
134
Modulation Characteristics
135
Ctcss
135
Microcontroller
135
Test Standards
136
European Telecommunication Standard
136
DTI CEPT Recommendation T
136
Telecommunications Industry Association
136
Product Codes
137
T858/859 Fault Finding
265
Default Chapter
268
General
268
PA Faults
268
Voltage Chart
271
Fault Finding Charts
272
T858 Pa
272
T858 Power Control
273
T859 Pa
274
T859 Power Control
275
T859 Fan Control Circuitry
276
Removing the PCB from the Heatsink
279
Part G System Configurations
323
1 T855 Link Selectable Features
325
Flat or De-Emphasised Response
325
Mute Selection
325
Receiver Disable
325
CTCSS Configuration
325
300Hz High Pass Filter
326
Audio Processor Links
326
General
326
Audio Processor Linking Details for CTCSS
327
2 T856/857 Optional Features
329
Audio Processor
329
Link Details
329
Typical Options
330
Line Transformer Inputs and Outputs
330
Opto Key
330
Relay Driver
330
3 Talk through Repeater
333
4 Line Controlled Base Without Talk through
335
Transmitter Tail Timer
336
4
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Tait T858 Specifications
General
Brand
Tait
Model
T858
Category
Accessories
Language
English
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